Sapper

A sapper, in the sense first used by the French military, was one who sapped another's fortifications. A sapper is an individual in military service, often called a military engineer nowadays, who may perform any of a variety of tasks, under combat conditions. Such tasks typically include bridge and road construction; and mine laying, or detection and clearing. In other words, the sapper's tasks now involve facillitating movement of allied forces, and impeding movement of the enemy's.

When castles served a military purpose, one of the tasks of sappers was to weaken the bases of castle walls to enable them to be breached--before means of thwarting these activities were invented. Broadly speaking, sappers were originally experts at demolishing or otherwise overcoming or bypassing fortification systems.

Sapper (abbreviated Spr) is also the Royal Engineers' equivalent of Private.