vulcan 5 (2017) 42-63 brill.com/vulc 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 mobil- ity. 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 It is a story about how a military deci- sion came to be outdated long before it was upgraded.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 intro- duced 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 © koninklijke brill nv, leiden, 2017 | doi 10.1163/22134603-00501004Downloaded from Brill.com09/25/2021 03:41:21AM via free access <UN> 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 devel- opments 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 forc- es as an independent service branch covers a wider time frame and presents technological and organizational developments in Sweden within a frame- work of international tank technologies (Kjellander 1992). The international perspective had been presented earlier both in the interwar period and lat- er (Bratt and Lindblad 1935; Berge 1966). Those surveys treat tanks from an vulcan 5 (2017) 42-63 Downloaded from Brill.com09/25/2021 03:41:21AM via free access <UN> 44 Wulff 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 compila- tion was further elaborated in another anniversary book, now celebrating 90 years of tanks in S weden (Lindström and Svantesson 2009), though this anni- versary 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 com- mented 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 ef- forts 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 plan- ning 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 ap- proach 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 Downloadedvulcan from Brill.com09/25/2021 5 (2017) 42-63 03:41:21AM via free access <UN> 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 interna- tional 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.