The force and mobility of the attack depended on the commitment of Germany's latest weapons and armored fighting vehicles. At the beginning of World War II, the German army had led the world in mechanized warfare tactics, overwhelming enemies repeatedly with their rapid Bewegungskrieg or "Blitzkrieg" tactics of combined warfare. Late in the war, the Germans had developed a number of advanced armored vehicles. The Tiger II, Panther and Jagdpanther were armed with new, high velocity 8.8 cm KwK 43, and the 7.5 cm KwK 42 cannons. Due to the flat trajectory and greater armor penetration of these guns, and the fact that thicker armor was used to shield them, German tanks enjoyed a superiority in firepower over nearly every American vehicle in use. Despite their superiority, the advanced German tanks were few in number and often experienced breakdowns because of unreliable mechanical parts.