As discussed earlier, there were three British engineering units present, the Royal Engineers, the Royal Military Artificers (the Royal Sappers and Miners from 1812) and the Royal Staff Corps. Theoretically there was a distinction, in that the role of the Royal Engineers was for static defences i.e. the attack and defence of fortresses whilst mobile work was the responsibility of the Royal Staff Corps i.e. field works and bridging. There is still a debate going on about bridging, as the perceived view is that it was primarily done by the RSC. My research indicates that the Royal Engineers did most bridging work. There is a difference in that the Royal Engineers tending to do most destruction whilst the Royal Staff Corps were more involved in construction. What is apparent is that the officers from the different corps did share information and experience for the benefit of all. The picture of the bridge at Ponte de Murcella comes from Douglas’ book on military bridging. Identical pictures are in the contemporary notebooks of Engineer and Staff Corps officers (Burgoyne, Scott and West).

What all the engineer officers faced was a lack of resources, both in men and materials. This meant that river crossings often had to be made with whatever material was available. At its simplest this could be preparing the banks and bed of a river for fording. For smaller rivers and smaller loads, pontoons or boats could be rowed across, sometimes with lines to keep them in place.

The real challenge came when large bodies of troops or heavy loads needed to cross big rivers. Here the nature of the river determined the bridging methods that could be used. Flying bridges, trestles, local boats, wine casks and pontoons were all used at different times. The most frequent method was probably the repair of an existing bridge. More often than not, temporary repairs were carried out using locally-sourced wood. There are many examples where the material obtained either from nearby woods or by dismantling buildings. The two most impressive examples of this during the war were the repair to the stone bridge at Alcantara in 1812 and the crossing of the Adour in 1814. The repairs to the bridge at Alcantara (and also Almaraz) were designed by Henry Sturgeon and Alexander Todd of the Royal Staff Corps. The design is described by Andrew Leith-Hay:

The arch destroyed was of so extensive a span, and the parapet of the bridge so great a height from the bed of the river, that no repair by using timber was practicable; the gap to be passed over being ninety feet wide, and the height of the bridge, one hundred and eighty from the bed of the river … The work was commenced by placing two beams on supporters four feet high and ninety feet asunder. These were secured to the side and end walls of the building by braces and tackles, to prevent their approximating by the straining of the ropes. Eighteen cables were then stretched round them, extending from end to end; eight pieces of timber, six inches square, at equal distances, were placed upon the ropes, with notches, one foot asunder, cut on their surface to secure them; these notches were seared with hot irons to prevent the ropes from chafing. The cables were then lashed to the beams; they were netted together by rope-yarn, and chains of sleepers were bolted and laid on the network, and secured to the two beams originally placed at the extremities of the work. Planks were cut and prepared for being laid across, bored at the ends so as receive a line destined to secure them to the sleepers and to each other … The next point was to prepare the edge of the fractured part of the bridge, and to cut channels in the masonry for the reception of the purchases. When arrived on the spot, four strong ropes were stretched from side to side, as conductors, for passing the cable-bridge across, the beam on the south side having been previously sunk into the masonry; the whole was then stretched by windlass erected on the opposite pier, by which means it was so tightly drawn as to prevent any great sinking, or the vibration which might render it insecure and dangerous, even when heavy weights were passed over.³