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
Trench warfare has been infrequent in recent wars. When two large armoured armies meet, the result has generally been mobile warfare of the type which developed in World War II. However, trench warfare reemerged in the latter stages of the Chinese Civil War (Huaihai Campaign), the Korean War (from July 1951 to its end), and at Dien Bien Phu and other later locations and engagements during the Vietnam War. During the Cold War, NATO forces routinely trained to fight through extensive works called "Soviet-style trench systems", named after the Warsaw Pact's complex systems of field fortifications, an extension of Soviet field entrenching practices for which they were famous in their Great Patriotic War (the Eastern Front of World War II).