Civilian Structures As Military Restrictions the Sudden Transition to Heavy Tanks in Sweden

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Civilian Structures as Military Restrictions The Sudden Transition to Heavy Tanks in Sweden

Petter J. Wulff Apeltunet 7, 181 48 Lidingo, Sweden [email protected]

Abstract

The military community is a secluded part of society and normally has to act on the conditions offered by its civilian surroundings. When heavy vehicles were developed for war, the civilian infrastructure presented a potential restriction to vehicular mobility. In Sweden, bridges were seen as a critical component of this infrastructure. It took two decades and the experiences of a second world war for the country to come to terms with this restriction. This article addresses the question as to why Swedish tanks suddenly became much heavier in the early 1940s. The country’s bridges play a key role in what happened, and the article explains how. It is a story about how a military decision came to be outdated long before it was upgraded.

Keywords tanks – infrastructure – transition

In the 1920s and 30s, Sweden produced and imported various forms of armored vehicles—primarily so-called ‘tanks’—which had been spectacularly introduced in The Great War. In the case of tank technology, however, a sudden shift occurred in the early 1940s. Within a year Swedish tank weights doubled and never returned to earlier levels. Such a drastic shift is not a normal part of technological development, or at least cannot be explained by any sudden change in tank technology itself. The sudden deviation from a more gradual development path calls for an answer as to what made the shift occur. That is the problem investigated here. It turns out that the shift in tank weight can be understood if seen as related to the civilian infrastructure, with bridges as the

Civilian Structures as Military Restrictions 43 critical component. As a starting-point let us look at what has been written about the early Swedish tank development.

The Swedish Tank Literature

The Swedish tank literature (rather inaccessible to an international audience, being mostly in Swedish) is summarized here. The first decades of tank developments have been treated by Stade (1970; 1972), but his story ends just before the transition from light and medium tanks to heavy tanks, which is the theme of this article. He notes that in 1938, only a year before the outbreak of World War ii, Sweden had hardly a single tank fit for field duty (Stade 1970, 119) and his research sought to explain this remarkable fact. In their early phase, tanks were classified with regard to weight: a “medium” tank weighed in at 10–25 tons, while “light” and “heavy” categories were de- fined by simply being below or above that range, respectively (Stade 1970, 121). Sweden entered into many international contacts, with tank officers visiting, most importantly, Germany, France, Czechoslovakia, and Austria, and the first three of those countries all sold tanks to Sweden. Austria had a tank expert, Fritz Heigl (author of the 1926 Taschenbuch der Tanks), who made drawings for what was intended to be a Swedish tank model, but his design was never real- ized (Stade 1970, 126–132). The close links to Germany in the 1920s regarding tanks and aircraft have been investigated by Wulff (2005). Like Stade, Wulff (2006a) has treated Sweden’s overall tank development in the interwar period. He has tested whether the development could be seen as an application of the principle of “elastic defense,” a principle launched by the Social Democrats in the mid-1920s and taken up again as a Swedish defense principle in the 1990s. It argues that defense technology in times of low threat should be experimental (with few units acquired of many models), but should switch to mass production (with many units of few models) when the threat rises (Wulff 2006a; 2006b). Brännström (1990) takes up another perspective in arguing that the Swedish interwar tank program was the result of a response to the development of anti-tank weapons. An anthology celebrating the fiftieth anniversary of Sweden’s armored forces as an independent service branch covers a wider time frame and presents technological and organizational developments in Sweden within a framework of international tank technologies (Kjellander 1992). The international perspective had been presented earlier both in the interwar period and later (Bratt and Lindblad 1935; Berge 1966). Those surveys treat tanks from an

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organizational as well as a technical and tactical perspective. Here under- standing their development with respect to civilian infrastructure offers a more integrative assessment of technological development and deployment in the Swedish military. The 1992 anthology also has a compilation of S wedish tank model data; a theme with parallels in booklets appearing around the same time (Porat 1989; spf 1992a; 1992b; 1992c; 1992d). The tank data compilation was further elaborated in another anniversary book, now celebrating 90 years of tanks in S weden (Lindström and Svantesson 2009), though this anniversary arrived somewhat prematurely, as the first tank only arrived in Sweden in 1921. A few of the major themes mentioned in the literature should also be commented on. Stade highlights interservice rivalry as an important factor, linked to tank materiel being placed in the hands of the artillery, whose representa- tives were reluctant to accept new tank models. They tended to prefer light tanks, and one argument from the artillery was that road bridge capacities im- posed a weight limit of as little as 6–7 tons (Stade 1970, 125). There was also an interservice rivalry with the cavalry, which was developing armored cars at the same time. Rivalry in the 1920s has also been attributed to the tension between the general staff and the tank officers (Brännström 1990, 86, 93). The least that can be said is that there was a sincere lack of coordination of development efforts in tanks in the early years (Wulff 2006a, 84–91). Quite beyond the rivalry between departments, there was a question of whether the tank was even suited for Swedish forces at all. There was a skepti- cism about tank performance in Swedish terrain (Brännström 1990, 93; Cronen- berg 1982, 352; Lange 1992, 11). The argument was used even before any tank had reached Swedish soil (Brännström 1990, 82). A variant of this argument was that Sweden’s type of terrain allowed for fewer tanks than were needed by other nations (Stade 1972, 38).

Theory and Method

An idea often underlying texts on military matters is that doctrine and planning activities explain much of why weapon systems are developed as well as their main features. Another approach, employed here, uses social history to investigate the development and deployment of military technology. This approach asks questions like, “How do social and cultural environments within the military itself or in the larger society affect military technological change?” (Hacker 2008, 1). In this case, the development of Swedish tanks can be seen as at least partially the result of socio-cultural factors relating to interservice

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Civilian Structures as Military Restrictions 45 rivalry and communication problems between military and civilian cultures. The approach also fits into a broader theoretical framework called the Social Construction of Technology, or scot (Bijker, et al. 2012), although the question of communication problems may not be a main theme there. The text here has a character of quantitative analysis presenting technological trajectories. It is an approach to tank development more thoroughly elaborated in an international overview by Castaldi et al. (2009), but while they plot “mobility” against “battlefield capability”, here the consideration is “mobility” vs. “weight”. A further methodological comment should be made. There is an ambi- tion to present the problem in such a way that today’s decision-makers may learn something from it. This calls for a certain emphasis on general features and less on specific individuals, dates, tank models, and place-names. A story along those lines can hopefully help us see parallels between the past and the present.

Tanks—Some Background Comments

The tank was originally developed in Great Britain during World War i. Other nations soon followed, and in the 1930s tanks had been incorporated into the armed forces of more than 30 countries. Leading producers of the tanks for many of these countries were Great Britain and France. As indicated above weights ranged from light tanks of below 10 tons to heavy tanks of more than 25 tons (Bratt and Lindblad 1935, 108–113), Sweden had acquired light tanks first from Germany and then from France before engaging in the production of somewhat heavier domestic models in the late 1920s. Tanks were developed to move in terrain. They could also move on roads, but there the wheeled armored car had superior speed. To combine the ad- vantages of the two types, developers came up with a vehicle that could shift from caterpillar treads to wheels. Sweden was among the countries producing such a hybrid. This kind of vehicle, falling between the infantry´s traditional tank and the armored car of the cavalry, had no clear organizational backing and was only produced in a single unit (Wulff 2006a, 79). As the double trac- tion systems tended to make the hybrid heavier than a tank with an equivalent firepower and armor protection, the weight restriction of the interwar period may have influenced the decision not to continue the production of hybrids in Sweden. The infantry’s tendency to tie the tank to the tactics of foot soldier weakened in the 1930s when the speeds of Swedish tanks more than doubled. A similar pattern can be discerned for the major powers of France, Germany, Russia, and the uk (Castaldi et al. 2009, 557–558).

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A Tank Weight Decision Taken

The tank weight question arose in the middle of the 1920s, when the general staff of the Swedish military asked the National Road Board (nrb) about the load capacity for tanks of the existing Swedish bridges. The nrb’s first answer was that 9 tons would be an upper limit. This reply was not, however, satisfac- tory, as the tanks acquired by the military to that time (the model m/21 with a 65 mm gun and speed of 16 km/h; See Appendix i) already weighed almost 10 tons. The weight limit was then reconsidered by the nrb and a new limit of 12 tons was suggested with the caveat that certain precautions were to be taken to accommodate this greater weight. By December 1928, the Swedish general staff, now content, had the 12-ton limit set down as a requirement for new Swedish tanks (Gillner archive 1928, 3/12). At the same time, there were also new developments happening in S weden’s road infrastructure, which would also have to accommodate the movement of armored vehicles.Although Sweden had a road system of “highest international class” by the end of the nineteenth century (Ahlström 1985, 37), road building was traditionally a local undertaking, where the peasant popula- tion catered to their own local needs. Much of this changed in the 1920s, and so that period has come to be seen as a decade of a “road revolution” (Pettersson 1988, 38). By the middle of the 1920s, the state assumed growing control over the road infrastructure with the aim of “developing nationwide uniformity and technically advanced road construction and maintenance” (Pettersson 1988, 173). This can be seen as a response to growing civilian demands on the road system. It has also been pointed out, however, that there was organized lobby- ing by the Swedish Road Federation, an interest group pushing for road mod- ernization (Blomkvist, 2001, following Seely 1987 on the u.s. situation). In any case, not only did the number of civilian vehicles increase rapidly in the 1920s and 1930s, but the weight per goods-carrier increased as well. Figure 1 shows a five-fold increase in the number of lorries during the interwar period, and— even more interesting—it shows more than a doubling of the load capacity per lorry. If the load on average was one ton in the early interwar years, that average load more than doubled to about two and a half tons by the end of the period. At the same time the figure shows that lorry weights only increased marginally in the 1920s. Part of this story is that of the development of the second generation of automobiles in the period, but there is no ‘pause’ in that development that can explain the flat weight curve that jumps up after 1929. The delayed rise of the weight curve could be an indication that the road system up to that point could not accommodate more than moderately loaded

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Civilian Structures as Military Restrictions 47

6.0 Nr of vvehiclesehicles 5.0 Weight/vehicleWeW ight/vehicle

4.0

3.0 [1923 = 1.0] Rate of increase 2.0

1.0

0.0 1923 1925 1927 1929 1931 1933 1935 1937 1939 Year Figure 1 The relative number of lorries and their average weight in the Interwar period. Source: Krantz 1992, 212–13.

vehicles, even while it was accommodating a steady increase in their numbers. The technically more advanced roads constructed from the mid-1920s permit- ted weights per vehicle to increase.

A Time for Bridge-Building

As integrated parts of the road system, bridges had to be adapted to the new conditions, and many new bridges had to be built. From the early 1930s on- wards, the number of bridges increased markedly. Figure 2 shows the bridges in Sweden built of three different materials—stone, steel and concrete—over a span of almost 100 years, from 1899 to 1988. The dominant building mate- rial for Swedish cart/lorry/foot bridges prior to 1900 was wood or stone. Only a tiny fraction of the steel bridges and almost no concrete bridges had been built before that time. This does not, however, include railway bridges, where steel construction came earlier. The number of steel and concrete bridges was still limited to less than approximately 15 percent of all bridges when the 12- ton tank limit was established in the late 1920s. A decade later the number of steel bridges had trebled, and the number of concrete bridges had risen even more rapidly, and by the late 1930s, they together represented about half of all

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% 100 90

70 Stone 60

50 Steel 40 Concrete 30

0 1899 1902–05 –08 –11 –14 –17 –20 –23 –26 –29 –32 –35 –38 –41 –44 –47 –50 –53 –56 –59 –62 –65 –68 –71 –74 –77 –80 –83 –86 –88 Ȧr

Figure 2 The 1930s was a time for bridge building. The vertical axis represents the percent- age of stone, steel and concrete bridges had been built by a certain year. In 1929 for instance, 85% of all stone bridges but only about 5% of all concrete bridges (existing in 1988) had been built. A steeply rising curve indicates a period of intense bridge building. Source: von Olnhausen 1991, 40. bridges (extrapolated from von Olnhausen 1991, 39). One could say, that a new bridge system had taken shape. There were civilian reasons to look into the load-carrying capacity of these bridges. We have already noted a general trend for lorries to demand more of bridge capacities. but the most extreme civilian demand on bridges seems to have come from the very vehicles constructing the new road network, including road scrapers and road rollers. As across much of the globe, the interwar period and Great Depression was a time of unemployment in Sweden and road building was one way for the State to create jobs. There was no need to slim down the workforce. Work could be carried out with roadbuilding machines having a tall, ironclad silhouette, not unlike that of a tank (Figure 3). In fact, when new regulations for steel bridges were suggested in 1935, a 15-ton road roller was chosen as the standard maximum load, except in more desolate, less travelled areas. If regulations for new bridges tended to allow for heavier vehicles, what of the existing bridges? Here new calculation methods indicated that a 30 percent increase on earlier limits would be feasible. The 1935 regulations pointed to the possibility of test-loading bridges in doubtful cases to determine their load-carrying capacity (sou 1935: 7, 22). The conclusions and comments of the investigation might have been expected to initiate a reconsideration of tank options, but interestingly, in this case, the 12-ton vehicle limit remained. Thus, it appears that the road network was built and rebuilt to standards that had little to do with military planning.

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Civilian Structures as Military Restrictions 49

Figure 3 A road-building machine and its crew in Sweden around 1930. Photo by Gustav Vennerholm; Courtesy of Västergötlands Museum, Sweden.

In the road construction standards and rationale, there was only a passing reference to military vehicles, and tanks were not mentioned at all (sou 1935: 7, 11). This is rather strange as there were people with military titles in the expert group presenting the suggestions, yet there seems to have been no explicit military rationale proposed for the new road system. Indeed, one member of the roads committee was Maj. Ernst Nilsson, on whose investigations the group’s conclusions were essentially founded (sou 1935: 7, 5). He and at least one other member belonged to the Väg- och vattenbyggnadskåren (Road and Water Construction Corps), which itself had military roots.

Tank Alternatives

If Swedish bridges by the mid-1930s were found to be capable of carrying 15 tons, was it a matter of great consequence to tank technology or not? A good place to look for an answer is a state-of-the-art treatment of the tank question that appeared as a 1935 booklet written by two Swedish tank experts. This booklet summarized the knowledge for Swedish military planners in the 1930s regarding the development of armored vehicles up to that time. They stated

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50 Wulff that the weight range of between 10 and 25 tons was “the backbone of modern armored units” (Bratt and Lindblad 1935, 32–33). Such vehicles were, according to the authors, well suited to encounter enemy tanks, other armor-protected weapons, artillery, and anti-tank weapons. Swedish tanks at the time were only marginally within the weight range recommended by the experts because of the existing 12-ton limit. However, the 10- to 25-ton recommendation implied that there were alternatives to be considered. Rather oddly, the two experts could not present much substan- tial evidence in favor of the 10- to 25-ton range. In an appendix listing tank types from around the world, an English 18-ton tank and a Japanese 14-ton vehicle are about the only examples well within the “backbone” range. Germany, which might have supplied some of the arguments for the 10- to 25-ton recommendation, was conspicuously missing from the list.1 This omission was possibly made for political reasons, as the Swedish Social Democrat government wanted to disengage itself from all connections with the 1930s Nazi Germany. The English example mentioned in the report was probably a variant of a 16-ton tank that the Swedish military attaché in London had reported on in 1930. It was then said to be “considerably superior” to other English tanks in fire rate and impact on target (Uggla 1930, 9/12). With regard to England’s leading status in tank development in the 1920s—and the type’s being close to a 15- ton limit—it would seem to have been an alternative that Sweden might have considered acquiring. The section on tank capabilities in the 1935 booklet included movement across dikes and through shallow water, but the problem of crossing bridges was not mentioned at all, even though it was the initial reason for the Swed- ish weight limit. Furthermore, there was no comment about the tanks heavier than the “backbone range,” which by that time were in use by both England and France.2 It might have been asked how those leading powers could go so far beyond what was permissible in Sweden.

1 Although prohibited in building them by the Treaty of Versailles, Germany did build various vehicles that were clearly tanks. The 1929–33 Leichttraktor (Vs.Kfz.31) and the Panzer i and ii of the mid-1930s were all under 10 tons, but by 1934 the Germans had designed the 23-ton Neubaufahrzeug that mounted a 37 mm cannon, the same size and armament as the Pan- zerkampfwagen iii designed in 1935–37 and put into service in 1939. 2 For example, the Vickers Independent A1E1 was a 34 ton, multi-turreted, 370hp tank developed between 1924–26 that boasted a 47 mm quickfiring 3-pound gun and four .303 machine guns. Although the A1E1 was only deployed as a unique prototype that was retired in 1935, its size and armaments became the basis for the generation of British (and Soviet) tanks developed in the 1930s.

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Civilian Structures as Military Restrictions 51

In this politically and economically tumultuous time, Sweden faced distinct problems in trying to purchase tanks abroad, but there was also the option to develop a domestic tank. Sweden was quite well equipped to do so. Beside the tank-producing company Landsverk (which was built up and run by German specialists), there were also manufacturing giants Bofors and Volvo. Both had contributed in the development of an armored car in the early 1930s: Bofors with expertise in armor, and Volvo with expertise in chassis construction and transmissions. Actually, Landsverk went on to produce a 16-ton tank prototype, which was ready just before World War ii broke out. But with the 12-ton rule still in force in Sweden, the tank model was intended for export. It was used by the Hungarian army, the very force that had asked Landsverk to produce it (Lindström and Svantesson 2009, 50).

Bridge Alternatives

There was one category of bridges, however, that was designed for much heavier loads than we have been considering so far: railway bridges. Even if there were challenges in combining train and tank traffic, the capacity for tanks to ride along on rails was a possibility envisaged in at least one Swedish tank proj- ect of the time. This innovation, however, never materialized (Lindström and Svantesson 2009, 11–12). A defense commission report of 1935 stressed the importance of the railway bridges in northern Sweden, where the country’s largest rivers cut across the country west to east. The rivers were seen as formidable barriers against a So- viet advance from the north, provided the advancing force did not capture the bridges (sou 1935: 38, 151). How this related to tank movement, however, was not discussed, once again showing how overall strategic military planning and tank movements seem not to have been explicitly enunciated by those considering tank developments. One traditional task for military engineers was the building of temporary bridges. Swedish military bridges of the late 1920s were designed to both fit and carry existing tanks (Khgn 1929, 76) and new regulations issued in 1934 did not change that. Bridges were expected to carry up to 12 tons, just as the weight limit for the tanks remained at 12 tons (Berg 1937, 69, 80). Only with the advances of the German army in 1940 was there a call for sub- stantially increased carrying capacities for bridges. Blitzkrieg was the word of the day, and in an article on the concept and its implications for the Swedish engineering troops, it was proposed that they, too, should transform into Blitz troops along with the rest of the army (G.H.H. 1941). The article was based on

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52 Wulff a contemporary u.s. manual on river crossing equipment, perhaps because of a lack of information from German sources. It appears that in 1938 the Ameri- cans had a model bridge capable of carrying 20-ton loads and that it had been complemented in 1940 with a model capable of taking an even larger load of 25 tons (G.H.H. 1941; 14, 20). The author of the article saw that as a reasonable range for Sweden to aim for as well (G.H.H. 1941, 22). This would mean development of a bridge capability corresponding to the weight of the heaviest tanks envisaged. That is, the engineering equipment was no longer to adapt just to existing vehicles but rather to anticipate what needs and load capacities were to come. It was a way of facilitating the acquisition of much heavier tanks. The existing Swedish bridge equipment was found to be outdated and in need of complete renewal (G.H.H. 1941, 14, 21, 22). Therefore, the author de- clared that ‘Blitzkrieg’ was to the Swedish engineering troops, “nothing less than a revolution” (G.H.H. 1941, 38). In one tightly packed sentence he explained to his brothers in arms how the connections built or maintained by them,

suddenly take a leap towards increased intensity as well as increased weight and increased velocity at the same time as the risk of disruption of the connections through bomb raids and parachute troops increase many times over and the demands from the Blitzkrieg command for rapid restoration become ever more insistent (G.H.H. 1941, 38).

There was not a single word about weight restrictions. A further alternative was to have tanks swim across rivers and lakes. The importance of tanks’ river- crossing capability had been indirectly acknowledged in the 1935 survey, which noted the existence of amphibious tanks in England, France, and the Soviet Union. Making tanks capable of locomotion in water environments was an ob- vious alternative to having them cross on civilian bridges. The fact that there was no weight limit for “swimming tanks” was demonstrated by the Swedish “Stridsvagn S” (Stridsvagn 103) developed in the 1960s. Its weight was three times the 12-ton limit, which by then, had been abandoned.

The 1930 Defense Commission

In 1930, a parliamentary defense commission was formed with members from all the political parties except the communists. It was a thorough undertaking with high ambitions to educate the members in security policy and military matters. There are minutes from almost 300 meetings that took place in the

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Civilian Structures as Military Restrictions 53 five years of the commission´s existence. The commission generated well over one thousand pages of reports (sou 1935: 38–43). During those years, the security policy situation of Sweden changed drastically. In neighboring Germany, a Nazi regime took over, disarmament efforts were halted, and what Winston Churchill (1948) later termed “a gathering storm” loomed. The commission was, therefore, less an environment for far-ranging experimentation with military equipment, and more one for increasing the number of units of existing models to improve readiness for war. Given that background, the 1930–35 defense commission must be credited with emphasizing the existing weaponry and recommending acquisition of bulk equipment and ordnance, including machine guns, mortars, and munitions (sou 1935: 39, 542). It might, however, be questioned whether it was reasonable of the commission to devote so few pages to equipment. The text addressing these issues makes up less than two percent of the more than 600 pages on the army, with the rest of the document centered on matters of personnel and organization. One argument presented for this disproportional treatment was that weapons technology, in principle, had not made much progress during or after World War i (sou 1935: 39, 538–39). This was an amazing pronouncement on a global conflict that had seen the emergence of tanks, air combat, and gas warfare. It was even more amazing, considering that the defense commission had been formed by a group of officers dedicated to technological quality before quantity. Their position seems to be a reaction against the army leadership, which had emphasized quantity, and it can be seen as part of a move to get political support from the parties in parliament that were traditionally skeptical of defense spending (Wulff 2008, 154–155). The commission could have taken up the facts and implications that surface in the booklet on tanks appearing shortly after their own report. It is conceiv- able that the 1935 booklet itself was published to present arguments favoring the tank to a broader audience after they had been neglected by the commission secretariat. An indication of this is that the resources for tanks suggested by an expert subcommission had been reduced from 40 to 30 vehicles (Stade 1972, 39).

A New Solution

It would take a new world war and its rapid German tank movements through Europe for Sweden to abandon the 1928 tank and bridge load limit. In May 1940, the tank “stood out sharply in the Battle of France—a battle involving more than one thousand tanks on each side—as the weapon of decision”

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54 Wulff

(Stolfi 1970, 1). Weights of major tanks on the winning German side ranged from 10 to 20 tons (Stolfi 1970, 19), which validated the soundness of the procla- mation in the 1935 tank booklet that 10 to 25 ton tanks would be the backbone of modern armored units. The events on the continent represented a new call for reevaluation of the Swedish weight barrier. This time the call was heeded. The reaction was not immediate, but six months after the German victory a letter was sent to the leading tank expert in Sweden in charge of tank acquisitions at the Army Ad- ministration, Lieut. Col. Eric Gillner. The letter was from Maj. Nils Gustaf D:son Aschan, at the Cavalry Inspectorate, who had also gone with Gillner to Prague to try to acquire tanks the year before. The letter was cautiously phrased: “On some occasion I have indicated that the opinions on the capacity of our bridges to carry tanks are in need of revision” (Aschan in Gillner Archive 1940, 1:19/11). The letter was also handwritten, giving it a personal character, but perhaps also depriving it of any official status. The wording of the letter may have been cautious, but the text was backed up by expertise. Aschan had discussed the possibility of a 20-ton tank with a military engineering contact, who in turn had contacted a leading bridge expert. The expert, in fact, was Maj. Ernst Nilsson, the person responsible for the recalculation of bridge capacities in the 1930s that led to raising the load limit. Nilsson was employed by the city of Stockholm and the man behind some of its major bridges. He has been called “one of Sweden’s most prominent bridge technicians” (Bergström 1949, 440–441). Now, in November 1940, he already had the answer as to whether Sweden´s bridges could take a 20-ton tank. He needed no more than two pages to reach his conclusion that 20-ton tanks would generally not have a problem using the existing Swedish bridges. There were, however, some qualifications. On new steel bridges the tank should keep to the middle of the bridge, and should not be immediately followed by another 20-ton tank. On older steel bridges, it was acceptable to pass but at low speeds. Stone and concrete bridges presented no problem, as the extra load of a tank was negligible in comparison to the weight of the bridge itself (Gillner Archive 1940, 1: 19/11, appendix 14/11). In other words, tanks as heavy as the Ger- man models could be used on Swedish bridges without much problem. Civil- ian and military expertise had, again, come together, as exemplified by the fact that the civil engineering bridge expert’s statement was attached to the letter addressed to the military tank expert. With the right question put directly to the right person, the administra- tive machinery got to work. In the spring of 1941, an armored committee was formed to propose vehicle types. It had the new weight limit adjusted to 22 tons. In June 1941, the army received permission from political leaders to order

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Civilian Structures as Military Restrictions 55 more than 100 tanks balancing on the new weight limit (Cronenberg 1982, 363). In 1942, it was decided to give the armored troops the status of a separate branch of the army, and to no longer be subordinated to the infantry, which allowed tank technology to proceeded in new directions. This it certainly did. One can almost imagine the relief of tank officers and development engineers when, in the early 1940s, they were allowed to expand tank resources beyond the constriction of the old weight barrier. The weight change is illustrated both in diagram form (Figure 4) and in the photo contrasting tank size before and after the change (Figure 5). During World War ii, Sweden acquired approximately 700 tanks, which is a remarkable achievement, or at least a striking con- trast to the interwar lack of development (Cronenberg 1982, 365–366). It may also be noted that in 1940 Sweden produced two armored trains that were far heavier than the tanks (Palmstierna 1982). An observation should be made about the correspondence that finally solved the weight issue: The person initiating the 20-ton question was a member of the cavalry inspectorate. Formally, this was odd, as the cavalry only had

1942–1960s 50

30 Weigth (tons)

20 1931–1941 1921–1929 10

0 0 10 20 30 40 50 60 70 80 Velocity (km/h) Figure 4 From slow, to fast, to heavy. Five decades of tank development in Sweden based upon data for the tank models found in Appendix i. The sudden weight transition discussed here occurred in the early 1940s between the 1941 and 1942 tank models. Source: Lindström and Svantesson 2009.

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Figure 5 Illustrating the weight transition: a 1942 tank model about to lift a 1941 model. Source: Lindström and Svantesson 2009, 53; Courtesy of Swedish Armor Historical Society. armored cars of moderate weight and their prime interest was speed more than weight. Tanks belonged to the infantry division, where a demand for heavier vehicles would more naturally have originated. However, the person in question had only recently moved from the infantry to the cavalry inspectorate. It is an interesting case of someone crossing the boundary between organizations, and between two organizations that had been rivals regarding armored vehicles. The decision-making in this case concerned both the military and civilian side of society. It took well over a decade before a dialogue was established between them about the validity of their original agreement in the mid-1920s. One might have thought that the two expert worlds would come more easily together, as the bridge-building experts did hold military ranks. However, this was just a remnant of the engineering profession’s military roots in Sweden. In the early nineteenth century, Swedish engineering education had been in military hands, and when the Swedish university system took over their education, the road and waterworks engineers retained their military titles. Until 1934 the bridge-building engineers did not even belong to the defense department (Smedberg 1937, 5). Their inclusion under that department alone was not enough to initiate a dialogue on the tank weight problem. The question may have been too technically specific to be noticed at levels where budgets were negotiated. Beside this communication problem, there are two reasons related to organizational culture why the decision to upgrade tank weights was not taken

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Civilian Structures as Military Restrictions 57 earlier. Generally, a decision that has been taken makes organizational life eas- ier, as a matter decided on no longer requires employees to spend intellectual energy or enter into further negotiations on the topic. Another reason for the delay is that we are dealing with a military organization, and it is not in their genes to question the words of superiors. The defense commission of 1930–1935 could have been a potential forum in which to discuss the weight restriction. The commission members represented virtually all the political parties, and they were ambitiously given pre- sentations about all kinds of military problems. Moreover, the key person of the commission, Helge Jung, who set its agenda was an army man who became Sweden’s first peacetime professional supreme commander after World War ii. Tanks belonged to the army, but loyalties in the army with respect to armored vehicles were split between the cavalry, which promoted armored cars, and the infantry, which promoted tanks. To bring up a subject of such divided opinion before the commission members would probably not have strengthened the army vis-a-vis the navy. Better then—from an organization-centered perspective—for the army to concentrate on arguing against the navy by promoting the air force; a theme discussed elsewhere (Wulff 2008).

Conclusion

This is a story of infrastructure imposing restrictions on a social group, namely the Swedish army, and on their technological artifacts, tanks. The case presented here indicates that bridges may not be quite as permanent as seen to be by Winner in his famous article about how artifacts can freeze political decision- making for decades (Winner 1980). For one thing, there is a physical flexibility in the infrastructure being renewed over time. Apart from that, as we have seen here, conceptions about bridges’ capacities may even change without the physical structures themselves changing. First, some words on physical flexibility. The Swedish system of road bridges underwent a rapid transformation in the 1930s. Car and lorry traffic had increased markedly and Sweden was seen to need more and better roads. The very road-building activity also introduced heavy vehicles calling for new load- carrying capability of bridges. The new materials of steel and concrete facili- tated more robust bridge-building endeavors. There was also a conceptual change. Recalculations made on existing bridges showed that the 12-ton vehicle weight limit, hesitantly accepted by the road and bridge authority in the late 1920s, could feasibly be raised to 15 tons.

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The main person responsible for the recalculations was a major, or at least he bore a military title. That did not, however, mean that the military community quickly took up his recommendations. The 12-ton limit had been founded on the best available knowledge of the time and was, therefore, confidently laid down as a basic requirement on tanks. The concept of infrastructural per- manence possibly contributed to the confidence. Although many aspects of the armed forces were studied during the five-year work of the defense commission between 1930 and 1935, tanks were only marginally commented on in the final report. This was partly because questions of army equipment were subordinated to questions of personnel and organization, and partly because, with regard to equipment, there was an emphasis on quantity rather than quality. Thus, the concept of a 12-ton weight limit was not challenged at that time. Here it may be noted that bridges were also seen to constrain tank weights in the United States and the Soviet Union. In the u.s., tanks were limited to 15 tons in order to be within the limits of average highway bridges (us War Department 1922). In the Soviet Union, an 8-ton limit was proposed to comply with the capacity of “bridges on strategic roads,” although they recognized that there should also be tanks heavier than that in the tank corps (Triandafillov 1929). This means that although both countries acknowledged that bridges could imply tank weight limits, they were both less constrained by those limits than Sweden. After the defense commission had drawn up the contours of the army and other services—and had had them largely accepted by the political majority— attention in the armed forces came to be focused on issues of implementation. Tank weight was a non-issue until the German rapid subjugation of France reopened the case of the weight limit. Then the 12-ton limit broke down, to be exchanged initially for a 20-ton limit and then a 22-ton limit, and subsequently by no limit at all. Bridges had completely ceased to be a civilian restriction on the military. The assumed limitation (or this case’s “reverse salient” in the lan- guage of scot; see Hughes 2012, 66–68) of bridges to heavier tank deployment had not been conquered as much as it had vanished. Hence, what had been a physical restriction with validity in the 1920s, was no longer physically valid as bridges had become stronger in the 1930s. But by then it had become a mental (self-)restriction. Only an impulse from abroad— an external imperative—could break it. The Swedish military understood the infrastructure as “cemented,” when the system was actually “moving.” The win- dow of opportunity for developing heavier Swedish tanks before World War ii was therefore missed.

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Civilian Structures as Military Restrictions 59

Appendix i: Tanks of the Swedish Armed Forces: The First Half Century

Most tank models below are given with a model year so that for instance, “Strv m/21” means a tank of model year 1921. “Strv” is short for Stridsvagn, the Swed- ish term for a tank.

Tank model Entered Weight Speed Armor (mm) Armament service (tons) (km/h)

Strv m/21 1922 9.7 16 4–14 2 × 8 mm machine gun Renault ft 17 1923 6.7 9 16–22 37 mm cannon Strv fm/28 1928 8.5 20 Up to 34 mm 37 mm cannon Strv m/21–29 1930 9.7 18 4–14 2 × 8 mm machine gun Carden-Loyd Mk v 1935 1.4 45 6–9 6.5 mm machine gun Carden-Loyd Mk vi 1935 1.4 45 6–9 6.5 mm machine gun Strv fm/31 1935 11.5 75 6–14 37 mm cannon, 2 × 6.5 mm Strv m/31 1935 11.0 40 8–24 37 mm cannon, 2 × 6.5 mm Strv m/37 1938 4.5 60 6–15 2 × 8 mm machine gun Strv m/38 1938 8.5 45 6–15 37 mm cannon, 2 × 8 mm Strv m/39 1941 8.7 45 5–16 37 mm cannon, 2 × 8 mm Strv m/40L 1941/42 8.93 45 4–15 37 mm cannon, 2 × 8 mm Strv m/40K 1943/44 10.9 45 4–50 37 mm cannon, 2 × 8 mm Strv m/41 si 1942 10.5 48 8–25 37 mm cannon, 2 × 8 mm Strv m/41 sii 1942/43 Ca 11 48 8–50 37 mm cannon, 2 × 8 mm Strv m/42 tm 1943 22.5 42 9–55 75 mm cannon, 4 × 8 mm Strv m/42 th 1944 22.5 42 9–55 75 mm cannon, 4 × 8 mm Strv m/42 eh 1944 22.5 42 9–55 75 mm cannon, 4 × 8 mm Strv m/42 tv 1944/45 22.5 45 9–55 75 mm cannon, 4 × 8 mm Strv 81 1953 50 35 Up to 150 84 mm cannon, 2 × 8 mm Strv 74 1957 26 45 9–55 75 mm cannon, 2 × 8 mm Strv 101 1959 52 35 Up to 150 105 mm cannon, 2 × 7.62 mm Strv 102 1964 50 35 Up to 150 105 mm cannon, 2 × 7.62 mm Strv 103A 1967 37.7 50 20–40 105 mm cannon, 3 × 7.62 mm Strv 103B 1970 39.7 50 20–40 105 mm cannon, 3 × 7.62 mm

Source: Lindström and Svantesson 2009 and for Strv 103 armor: https:// sv.wikipedia.org/wiki/Stridsvagn_103.

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