A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility and tactical offensive and defensive capabilities. Firepower is normally provided by a large-calibre main gun in a rotating turret and secondary machine guns, while heavy armour and all-terrain mobility provide protection for the tank and its crew, allowing it to perform all primary tasks of the armoured troops on the battlefield.
Tanks were first manufactured during World War I in an effort to break the bloody deadlock of trench warfare. Originally made in the English city of Lincoln, their name was originally a shortened version of their code name "Water Carrier Mesopotamia". The shortened name was fashioned by the staff of Ruston's where they were first made. The British Army was the first to field a vehicle that combined three key characteristics: mobility over barbed wire and rough terrain, armour to withstand small arms fire and shrapnel, and the firepower required to suppress or destroy machine gun nests and pillboxes. Despite some success and a significant psychological effect on the German infantry, "the tank in 1918 was not a war-winning weapon."
Interwar developments culminated in the blitzkrieg employed by the German Wehrmacht during World War II and the contribution of the panzers to this doctrine. Hard lessons learned by the Allies during World War II cemented the reputation of the tank, appropriately employed in combined arms forces, as "indispensable to success in both tactical and strategic terms." Today, tanks seldom operate alone, being organised into armoured units and operating in combined-arms formations. Despite their apparent invulnerability, without support, tanks are vulnerable to anti-tank artillery, helicopters and other aircraft, enemy tanks, anti-tank and improvised mines, and (at close range or in urban environments) infantry.
Due to its formidable capabilities and versatility the battle tank is generally considered a key component of modern armies, but recent thinking has challenged the need for such powerful and expensive weaponry in a period characterised by unconventional and asymmetric warfare. Ongoing research and development attempts to equip the tank to meet the challenges of the 21st century.