The heroes (and sometimes the villains) in historical romances are often involved in war, whether in the Royal Navy, the army, or as spies. Even if their wartime activities do not appear directly in the story, their military experiences shape their lives and their characters. One group of unsung heroes in the army was the engineers. Engineer officers could not buy their commissions as cavalry and infantry officers did; they were only given commissions after training at the Royal Military Academy at Woolwich, and thereafter promotion was by seniority.
As you might expect, engineer officers were essential in sieges, planning where the trenches should be dug and artillery batteries sited, and also in repairing a fortress once it had been taken. Being an engineer in a siege could be as dangerous as being an infantry officer in the battalions attempting to scale the walls. The engineers knew their way through the trenches and where the weakest points in the walls were, and often led the way.
More interesting from the point of view of storytelling, however, are the other activities that engineers were asked to undertake. They could be sent off far ahead of the army, to make maps of the roads and the terrain, in the days when such things were not readily available. Other tasks included surveying the roads, rivers and bridges to see if the army could pass that way with all its artillery and baggage. They had to plan how to cross rivers where there was no bridge, either by finding a suitable place to ford it, or to build a temporary bridge. Without engineering officers and their reconnaissance journeys, the advance, or retreat, of an army would probably have involved many delays, backtracking and wrong turnings.
Engineers could also be left to blow up a bridge behind a retreating army. As Wellington spent several years advancing and retreating across Spain during the Peninsular War, it is quite likely that they were sometimes asked to rebuild bridges that their fellow engineers had demolished. All these activities give plenty of scope for contact with the enemy, spying, and other skulduggery and danger.
The illustrations are taken from A narrative of the Peninsular War by Andrew Leith Hay, available free as a pdf in Google books.
A good reference source for this topic is Wellington’s Engineers—Military Engineering in the Peninsular War 1808-1814, by Mark S. Thompson
There is an expanded version of this article on Myths, Legends, Books & Coffee Pots blog.