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 armour types 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 anti-tank rocket propelled grenades (RPGs) worldwide and its successors, the ability of tanks to operate independently has declined. Modern tanks are more frequently organized into combined arms units which involve the support of infantry, who may accompany the tanks in infantry fighting vehicles, and supported by reconnaissance or ground-attack aircraft. History Conceptions The tank is the 20th-century realization of an ancient concept: that of providing troops with mobile protection and firepower. The internal combustion engine, armour plate, and continuous track were key innovations leading to the invention of the modern tank. Many sources imply that Leonardo da Vinci and H. G. Wells in some way foresaw or "invented" the tank. Leonardo's late-15th-century drawings of what some describe as a "tank" show a man-powered, wheeled vehicle with cannons all around it. However the human crew would not have enough power to move it over larger distance, and usage of animals was problematic in a space so confined. In the 15th century, Jan Žižka built armoured wagons containing cannons and used them effectively in several battles. The continuous "caterpillar track" arose from attempts to improve the mobility of wheeled vehicles by spreading their weight, reducing ground pressure, and increasing their traction. Experiments can be traced back as far as the 17th century, and by the late nineteenth they existed in various recognizable and practical forms in several countries. It is frequently claimed that Richard Lovell Edgeworth created a caterpillar track. It is true that in 1770 he patented a "machine, that should carry and lay down