Trench warfare
Trench warfare occurred when a revolution in firepower was not matched by similar advances in mobility, resulting in a grueling form of warfare in which the defender held the advantage. On the Western Front in 1914–1918, both sides constructed elaborate trench, underground, and dugout systems opposing each other along a front, protected from assault by barbed wire, mines, camouflaged trapping pits, and other obstacles. The area between opposing trench lines (known as "no man's land") was fully exposed to artillery fire from both sides. Attacks, even if successful, often sustained severe casualties.
Trench warfare
A specialised group of fighters called "trench sweepers" ("Nettoyeurs de Tranchées" or "Zigouilleurs") evolved to fight within the trenches. They cleared surviving enemy personnel from recently overrun trenches and made clandestine raids into enemy trenches to gather intelligence. Volunteers for this dangerous work were often exempted from participation in frontal assaults over open ground and from routine work like filling sandbags, draining trenches, and repairing barbed wire in no-man's land. When allowed to choose their own weapons, many selected grenades, knives and pistols. FN M1900 pistols were highly regarded for this work, but never available in adequate quantities. Colt Model 1903 Pocket Hammerless, Savage Model 1907, Star Bonifacio Echeverria and Ruby pistols were widely used.