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
The French introduced the CSRG 1915 Chauchat during Spring 1916 around the concept of "walking fire", employed in 1918 when 250,000 weapons were fielded. More than 80,000 of the best shooters received the semi-automatic RSC 1917 rifle, allowing them to rapid fire at waves of attacking soldiers. Firing ports were installed in the newly arrived Renault FT tanks.