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
Between the two world wars many nations developed their own unique tanks and divergent theories of tank tactics, including the UK, France, the Soviet Union, Czechoslovakia, Japan, the US, and Italy. Though German tank development was restricted by the terms of the treaty ending World War I, Germany successfully combined their own tanks (plus Czech tanks from occupied Czechoslovakia) with infiltration tactics to produce blitzkrieg during World War II.