Appendix 4

Military Bridging

The Iberian Peninsula was a hostile environment for Napoleonic armies. Much of the country was covered with mountains, making traversing it difficult, if not impossible. In between the mountain ranges flowed wide and fast-moving rivers that could only be crossed by bridges or boats. Rain or snow in the mountains could raise the level of rivers by several feet overnight and sweep away any crossing-points. These rivers intersected the country and without a crossing-point an army could be faced with long marches to get from one side to the other. Where there were no mountains or rivers, there were plains; barren in the winter and baking hot in the summer. Roads were rarely better than rough tracks. The royal roads between major towns might be fully cobbled but these were very rare. The best normal road might have two lines of paving stones for wagon wheels but did not allow for passing. Most roads would be hard-packed earth, passable in summer but muddy in the winter. In all cases, maintenance was minimal. It was the geography as much as anything else that defeated Napoleon’s troops in Spain.

For nearly 2,000 years the Spanish had dealt with the major rivers by building strong bridges and knowing every crossing-point at the different seasons of the year. Several bridges built by the Romans still stood proud, such as those at Almaraz, Alcantara and Salamanca. Every campaign during the war relied to some extent on controlling, constructing or destroying bridges.

One of the Allies’ first tasks in 1808 was to establish crossing-points on the river Tagus in Portugal to allow rapid movement between the north and south of the country. Initially this was achieved through floating bridges (ferries) but later they were replaced by pontoon bridges. The boat bridges at Abrantes, Punhete and Villa Velha remained key crossing-points in all operations for the remainder of the war. These were carefully guarded and taken down whenever there was a threat from the enemy. Keeping these in place required constant attention and maintenance, as they were large structures. Lieutenant Harry Jones RE described the boat bridge at Villa Velha when he passed in December 1812. The breadth of river was 140 paces (105m); distance of boat to boat (centre), ten paces (8m). It was made up of twelve large and two smaller boats, each having two anchors. To ensure there was no interruption in its availability, ten boats were kept in reserve.¹ He similarly described the bridge at Punhete that was made of short, stout pontoons. The length of the bridge was 160 yards (150m), made up of twenty-one pontoons. The distance from centre to centre of the boats was eight yards (8m). These pontoons only needed one anchor, as the river was less rapid. Each of these had a permanent engineering presence and a guard.

As well as strategic crossing-points, bridging featured in operational campaigns. Moore’s retreat to Corunna in 1808/9 included the destruction of several bridges to delay the advance of the French. The destruction of the bridge at Castro Gonzalo (Benevente) led the repulse of the pursuing French cavalry and to a respite for the Allies. Several engineer officers were involved in destroying bridges and one, Lieutenant Davy, lost his life by misjudging his fuse. There was widespread concern in the Royal Engineers about the limited success in blowing-up bridges.

Wellington’s first success in 1809 was when he ejected Marshal Soult from the Portuguese city of Oporto. The French had destroyed the bridge there and to pursue them required a boat bridge to be rapidly built to allow the bulk of the pursuing Allied troops to cross. This was done using the numerous local boats that were employed in the wine trade. The 1809 Talavera campaign relied on control of bridges further up the Tagus at Alcantara and Almaraz, and by the end of the year both of these bridges had been made impassable and the nearest intact crossing-point was at Arzobispo, which is much nearer to Madrid than Lisbon. The French constructed a boat bridge at Almaraz but this was not possible at Alcantara due to the steepness of the valley and the speed of the river. The Royal Staff Corps built an additional temporary bridge over the river Tietar for the passage of Wellington’s army. The river was about 150 feet (50m) wide, which contained a deep channel about 70 feet (20m) wide. There were no pontoons or boats available in the vicinity:

The only material at hand was the timber from a large inn at about half a mile from the place … which was unroofed … a party of 500 men [taken from the line regiments] with saws and axes was sent to a distance of three miles to procure young pines to make [twenty] stakes.²

The main roof beams from the inn, 20 feet long and two feet square, were floated in the deep channel. Piles were then driven into the shallow part of the river using ‘large wooden mallets made on the spot’. The rafters and flooring from the inn provided enough decking to complete the bridge the whole held in place with ropes. This bridge was constructed in one day.

Whilst the major campaigns of 1809 to 1811 focussed on access to the major strategic bridges over the Tagus, smaller bridges were also used and discarded in the various operational campaigns. Wellington destroyed several bridges as the French army advanced through Spain into Portugal in 1810 as he retired into the Lines of Torres Vedras. Masséna did the same when he retreated the following March. As Wellington pursued him north he was faced with a number of obstacles. First the bridge over the Alva at Ponte de Murcella needed to be repaired. The Royal Staff Corps built a floating bridge as there was insufficient material to construct a full bridge. A few weeks later, Wellington needed a further crossing-point over the Coa near Almeida, Masséna having also destroyed this bridge. The Royal Staff corps, once again, made the bridge usable, using locally-sourced wood to fill the gap.

1811 saw major problems as the Allies now began to take the offensive. The focus of the operations moved further south and the crossing-points over the Guadiana now became more important, the only two major ones being under the castle at Badajoz and at Merida. The Allied sieges of Badajoz were seriously impeded due to the lack of a pontoon train and the difficulty in keeping the temporary bridges made from trestles, wine casks and pontoons in place in the changeable weather. Further north, when Wellington was threatened by a superior French army at the Battle of Fuentes del Oñoro, he arranged to have a temporary bridge built across the river Coa in case he needed to retreat.