Fort Vol. 2 1976 Planning versus fortification: Sangallo's project for the defence of Rome Simon Pepper Since 1527, when Rome had been captured and sacked by the mutinous soldiers of Charles V, it had been clear that the defences of the Papal capital were hopelessly outdated. The walls of the Borgo (the Vatican precinct) were constructed during the pontificate of Leo IV (847-855): those of Trastevere and the left bank, enclosing by far the largest part of the city, dated from the reign of the Emperor Aurelian (AD270-75) [1]. Impressive both for their length and antiquity, these walls were poorly maintained and fundamentally unsuitable for defence against gunpowder artillery. In 1534 the Romans were once again forcefully reminded of their vulnerability when a large Turkish fleet moored off the Tiber estuary. Fortunately the hostile intentions of the Turks were directed elsewhere: after taking on fresh water they sailed north to raid the Tuscan coastline. But in the immediate aftermath of the Turkish scare the newly elected Paul III committed himself to an ambitious scheme of re-fortification. Antonio da Sangallo the Younger, advised by many of the leading architects and soldiers employed by the Pope, was commissioned to submit design proposals [2]. Father Alberto Guglielmotti, the nineteenth-century historian of the Papal armed forces, tells us that Sangallo and his consultants decided to replace the Aurelian wall with a new line of works defending the developed areas on both banks of the river. The 18000 metre Aurelian circumfer- ence was to be reduced by half, a decision which is not difficult to understand when one glances at a contemporary map of the city. Mediaeval Rome was crowded into the Campo Marzio district — the ancient Field of Mars in the bend of the river — with village scale outposts in the Borgo, Trastevere and around the Lateran Palace. The fifteenth and sixteenth century additions extended north towards the Piazza del Popolo and east to the hi I Is—collectively known as the monti - where many Popes, among them Sixtus V, attempted to promote urban development. However, mediaeval and renaissance Rome together occupied only a small proportion of the fortified area. Other European cities contained sizeable areas of open land within their walls; but none rivalled Rome's 'urban countryside' dotted with ruins, farms, vineyards, villas and the strongholds of the nobility. Obviously this underdevelopment supported the case for drastic reduction of the circumference. Sangallo's team proposed a new circuit fortified by 18 immensely powerful double-flanked bastions, spaced at intervals of about 600 metres, supported by intermediate gun platforms (a type of blunt headed bastion). Guglielmotti's description is based in part upon accounts published by contemporary theorists, the best being that of Francesco de Marchi [3], and, in part, upon a Sangallo sketch showing an idealised version of the arrangement. Very little of this scheme was actually built. After 1542 it was decided to concentrate resources on the fortifications of the Borgo — the Papal enclave on the right bank which included 33 SIMON PEPPER Sangallo Bastion: Junction of curtain and flank. St Peter's Basilica, the Vatican Palace and the Castel San Angelo. By 1542 only one bastion had been finished near the Porta Ardeatina, at the southern tip of the circuit, another partly built on the north peak of the Aventine, and a third at a very early stage of construction on the south peak of the Aventine [4], However, the abandoned scheme made a profound impression upon the military architects of the period. As Horst De la Croix has recently pointed out, the prestige of the project attracted the interest of the entire military architectural profession, so that treatises published many years later contained references to ideas that first emerged from the 'conferences' convened by Paul III [5], Even in its reduced form it was probably the largest fortification project SANGALLO'S DEFENCE OF ROME Mini's Plan of Rome of 1551. (North is to the left): Leonardo Bufalini published one of the first printed maps of Rome in 1551, based on a measured survey hrtaken in 1534-35 in support ofSangallo 'sfortifiations. For a discussion of the plan and its origins see: Francesco Ehrle, La Pianta di Roma al tempo di Giulio Home 1911. SIMON PEPPER 36 Sangallo diagram illustrating the double bastion system: This cropped Sangallo sketch ( Uffizi, 942) seems to illustrate the early proposals as described by Francesco De Marchi. It is probably a theoretical diagram: certainly there is nothing to connect it with any Roman topographical feature. There are also significant differences between it and the competed Ardeatine Bastion. The acute-angled bastion tips of the diagram are expanded in the built scheme, giving more room for the face batteries (that is, the guns shooting away from the walls). The flank batteries, shooting along the walls, were also enlarged in the final scheme: the central 'platform' and demi bastions were eliminated. The Pozzi, well-shafts, Sangallo's drawing (Uffizi, 1505A) shows the lowest countermine level with the masonry tinted. Plan of countermine gallery and rampart sections. (Uffizi, 1362A). This could be called a working drawing, with dimensions, scale and set-outs to the existing Aurelian Wall. 161- L— 1 jritfW^h: ,Ct J" ^^ ,u 1 /^v-.vX. y^lL- .U^-v/vnV Three dimensional study of Ardeatine bastion: (Uffizi, U936A). The lower drawing is easily recognised as the completed bastion, although nothing remains of the free-standing cavalier, and the parapet details have been changed. The caption 'Per lafronte di S Antonino', refers to the sector before the Baths ofAntoninus Caracalla. The upper drawing is always catalogued as an aternative proposal for the same sector. However, it bears a strong resemblance to the hornwork on the Pincio which, viewed from the north, has a large round tower in mid-curtain, probably built over the Capozocha? SIMON PEPPER of a century which had yet to see the new city of Valetta or the great fortress of Palmanova. Moreover, the design of the completed bastion was most advanced. Scamozzi, Palladio's follower, writing in 1615 tells of 'that most famous bastion at Rome, with double flanks, both high and low level gun platforms, countermines, casemates and well-shafts, with a wall of such height and breadth that it cost a great deal of treasure' [6], Recently the vegetation which disfigured this bastion has been cleared away to reveal a most impressive if sombre, example of the forms evolved during the sixteenth century to resist the onslaught of gunpowder artillery. But the sophistication of Sangallo's design can best be appreciated from modern drawings which dissect the bland, brick-clad shapes to show the internal features mentioned by Scamozzi. Although the scheme itself was abandoned, some of Sangallo's drawings have survived. They are preserved in the Uffizi Gallery but, despite publication in facsimile by Enrico Rocchi in 1902, have attracted very little attention [7]. No doubt this is because they are strictly utilitarian documents; ranging from preliminary topographical studies through sketch layouts, to outline working drawings. As works of art they do not bear comparison with the bravura sketches of PIAZZA "O DELPOPOLO _ PORTA PI A CASTRO PRAETORIO CASTEL S ANGELO VATICAN, BORGO BATHS OF QUIRINALE DIOCLETIAN CAMPUS MARTIUS PALACE S MARIA MAGGIORE n POSSIBLE U ROUTE OF [] SANGALLO'S n SHORT WALL s croceC^ LATERAN NORTHERN AVENTINE SOUTHERN AVENTINE BATHS OF MONTE CARACALLA iTESTACCIO ^•poRTADI PORTA \ /f S PAULO ARDEATINA SANGALLO^\ DOUBLE BASTION 1000 2000m SOUTH I Roman fortifications. Key: A, Aurelian wall (3 rd century), B, Leonine wall (9th century), C, Sangallo's proposed circuit (1534-42), heavy solid line shows the route indicated on the Uffizi drawings, D, Paul Ill's Borgo fortifications constructed after 1542, probably part of 1534-35 scheme, E, Urban VIII's fortifications (1623-44). SANGALLO'S DEFENCE OF ROME Kline bastion. Key: A, Cavalier: an upper level gun platform. The cavalier must have had an access ramp, but no trace of it remains. B, piazza: an nm platform housing large pieces. C, vaulted bomb shelters. D, casemate: an enclosed gun chamber acommodating relatively small pieces of artillery, rraMvbreech loaders. E, magazine. F, ventilation flues. G, countermine gallery.. H, pozzi (well-shafts). J, countermine shaft. K, sally port. L, special ingle embrasure for fling at ground close to walls. pllo's 'double bastion' was highly esteemed for two feaures: the weight offlanking fire that could be brought to bear across a breach, and the istication of its underground countermines. In an emergency guns could be accommodated in each flank as follows: 2 small pieces at piazza level: 1 medium pieces mounted en barbette at both cavaliers. Thus, in a symmetrical system, four flanks and two cavaliers could generate a cross fire of Vis (see fig. 15). Mines offered an alternative means of attack against strongly armed works. Shafts would be driven beneath them and then, either ipsed by firing the pit-props, or exploded with even more dramatic effect. Countermines were devised to detect and frustrate such projects. Listening would be established at the end of each underground shaft: the sentry would be locked in with an ear-trumpet, candle, a drum with pebbles on it, and rlislening devices. Once a fix' had been obtained, the shaft could be extended towards the enemy mine which could be broken into by a raiding party l/stroyed by 'depth charges' laid ahead of it sandbagged, and fired by long fuses. Underground fighting varied very little from ancient times to the thes of the Great War. SIMON PEPPER Double bastion compared to other bastion plans: This diagram is a potted history of 16th century military architecture.