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.
Military history of Germany
By 1917 the German army had begun employing new infiltration tactics in an effort to break the trench warfare deadlock. Units of stormtroopers, were trained and equipped for the new tactics, and were used with devastating effect along the Russian front at Riga then at the Battle of Caporetto in Italy. These formations were then deployed to the Western front to counter the British tank attack at the Battle of Cambrai.