A tank is an armoured fighting vehicle designed for front-line combat, with heavy firepower, strong armour, and tracks providing good battlefield manoeuvrability. The first tanks were designed to overcome the deadlock of trench warfare; now they are a mainstay of modern ground forces and a key part of combined arms combat.
Modern tanks are versatile mobile land weapon system platforms, mounting a large-calibre cannon in a rotating gun turret, supplemented by mounted machine guns or other weapons. They combine this with heavy vehicle armour which provides protection for the crew, the vehicle's weapons, and its propulsion systems, and operational mobility, due to its use of tracks rather than wheels, which allows the tank to move over rugged terrain and be positioned on the battlefield in advantageous locations. These features enable the tank to perform well in a tactical situation: the combination of powerful weapons fire from their tank gun, and their ability to survive enemy fire means the tank can engage the enemy even under fire. In both offensive and defensive roles, they are powerful units that are capable of performing the key primary taskswhich are required of armoured units on the battlefield. The modern tank was the result of a century of development from the first primitive armoured vehicles, due to improvements in technology such as the internal combustion engine, which allowed the rapid movement of heavy armoured vehicles. As a result of these advances, tanks underwent tremendous shifts in capability in the years since their first appearance.
Tanks in World War I were developed separately and simultaneously by Great Britain and France as a means to break the deadlock of trench warfare on the Western Front. Their first use in combat was by the British Army in September 1916 during the Battle of the Somme. The name "tank" was adopted by the British during the early stages of their development, as a security measure to conceal their purpose (see etymology). While the French and British built thousands of tanks in World War I, Germany was unconvinced of the tank's potential, and built only twenty.
Tanks of the interwar period evolved into the much larger and more powerful designs of World War II. Important concepts of armoured warfare were developed; the Soviet Union launched the first mass tank/air attack at Khalkhin Gol (Nomonhan) in August 1939, and later developed the T-34, one of the predecessors of the main battle tank. Less than two weeks later, Germany began their large-scale armoured campaigns that would become known as blitzkrieg ("lightning war") – massed concentrations of tanks supported by motorised and mechanized infantry, artillery and air power designed to break through the enemy front and collapse enemy resistance.
The widespread introduction of high-explosive anti-tank warheads during the second half of World War II led to lightweight infantry-carried anti-tank weapons such as the Panzerfaust, which could destroy some types of tanks. Tanks in the Cold War were designed with these weapons in mind, and led to greatly improved armours during the 1960s, especially composite armour. Improved engines, transmissions and suspensions allowed tanks of this period to grow larger. Aspects of gun technology changed significantly as well, with advances in shell design and aiming technology.
During the Cold War, the main battle tank concept arose and became a key component of modern armies. In the 21st century, with the increasing role of asymmetrical warfare and the end of the Cold War, that also contributed to the increase of cost-effective Russian anti-tank weapons worldwide, the importance of tanks has waned. Modern tanks seldom operate alone, as they are organized into combined arms units which involve the support of infantry, who may accompany the tanks in infantry fighting vehicles. They are also usually supported by reconnaissance or ground-attack aircraft.