A pioneer is a soldier employed to perform engineering and construction tasks. The term is in principle similar to sapper or combat engineer.
1886 cigarette card depicting an Austrian pioneer
A sapper, also called a 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 defenses, and road and airfield construction and repair.
Modern sapper equipment
Soldiers of No 2 Field Company, Bombay Sappers and Miners on duty in China in 1900. The mule carries the tools required for field engineering tasks.
The fort of Ghazni which fell as a result of mining by a mixed contingent of the Bombay and Bengal Sappers during the First Afghan War on 23 July 1839.
A sapper of the Royal Engineers watches as soldiers reinforce security at FOB (Forward Operating Base) Shawqat in Afghanistan.