In World War II, the attack sequence of the previous war was reversed, in that making an initial breach in the enemy's defenses was usually entrusted to the artillery, infantry, and engineers, supported by dive-bombers when the opportunity offered. Once the breach had been made, tanks, accompanied by motorized and later mechanized infantry, poured through. Infantry were mounted in armored vehicles, such as half-tracks and Armored Personnel Carriers (APCs), to carry them quickly and safely along with the rapidly advancing armored divisions. Armored personnel carriers first appeared in large numbers early in World War II, when the Germans adopted them to carry the infantry contingents of their panzer divisions into battle. These vehicles, though only partly armored half-tracks, began the replacement of unarmored trucks for this purpose. After World War II many nations developed fully tracked carriers with all-around armor protection and a mounted heavy machine gun. The most modern infantry fighting vehicles are armed with an automatic cannon and antitank guided missiles. A typical mechanized infantry division is divided into five mechanized battalions and five armored battalions and has about 16,000 soldiers. 