In response to the threat of mobile armor, many countries had developed anti-tank guns, a form of towed, high-velocity artillery. These cannons fired armor-piercing rounds capable of penetrating the steel armor of tanks and incapacitating the crew inside. Further thinking focused on the possibility that tanks could also be used to fight enemy tanks. This resulted in a divergence of design in some countries, in which tanks were designed with either long-barreled small-caliber cannons capable of destroying other tanks, or with short-barreled, high-caliber howitzers used for direct fire infantry support. These two pre-war classes of tank were designated as Cruiser tanks and Infantry tanks in the United Kingdom and France, and were also present in early German panzers and assault guns. Some tanks, like the M3 Lee, were designed to fulfill both roles and were armed with two cannons.