sapper, also called pioneer or combat engineer, is a combatant or soldier who performs a variety of military engineering duties such as breaching fortifications, demolitions, bridge-building, laying or clearing minefields, preparing field defences, as well as working on infrastructure, road and airfield construction and repair. They are also trained to serve as infantry personnel in defensive and offensive operations. A sapper’s duties are devoted to tasks involving facilitating movement, defence and survival of allied forces and impeding those of enemies. The term “sapper” is used in the British Army and Commonwealth nations, the Polish Army and the U.S. military. The word “sapper” comes from the French word sapeur, itself being derived from the verb saper (to undermine, to dig under a wall or building to cause its collapse).

Sapper, in the sense first used by the French military, was one who dug trenches to allow besieging forces to advance towards the enemy defensive works and forts, over ground that is under the defenders’ musket or artillery fire. This digging was referred to as sapping the enemy fortifications. Saps were excavated by brigades of trained sappers or instructed troops. When an army was defending a fortress with cannons, they had an obvious height and therefore range advantage over the attacker’s guns. The attacking army’s artillery had to be brought forward, under fire, so as to facilitate effective counter-battery fire.

This was achieved by digging what the French termed a sappe (derived from the archaic French word for spade or entrenching tool). Using techniques developed and perfected by Vauban, the sappers began the trench at such an angle so as to avoid enemy fire enfilading the sappe by firing down its length. As they pressed forward, a position was prepared from which a cannon could suppress the defenders on the fort’s bastions. The sappers would then change the course of their trench, zig-zagging toward the fortress wall. Each leg brought the attacker’s artillery closer until the besieged cannon would be sufficiently suppressed for the attackers to breach the walls. Broadly speaking, sappers were originally experts at demolishing or otherwise overcoming or bypassing fortification systems.

An additional term applied to sappers of the British Indian Army was “miner”. The native engineer corps were called “sappers and miners”, as for example, the Royal Bombay Sappers and Miners. The term arose from a task done by sappers to further the battle after saps were dug. The saps permitted cannon to be brought into firing range of the besieged fort and its cannon, but often the cannon themselves were unable to breach the fort walls. The engineers would dig a tunnel from the forward-most sap up to and under the fort wall, then place a charge of gunpowder and ignite it, causing a tremendous explosion that would destroy the wall and permit attacking infantry to close with the enemy. This was dangerous work, often lethal to the sappers, and was fiercely resisted by the besieged enemy. Since the two tasks went hand in hand and were done by the same troops, native Indian engineer corps came to be called “sappers and miners”.