Tiger I was armed with a powerful 88mm gun (originally developed from 88mm Flak 36 L/56 gun) that made it a very dangerous opponent for any Allied tank, and its thick (but not shot-deflecting) armor made it virtually indestructible. Both the Sherman with its 76mm gun and T-34/85 stood a chance against Tiger only at close range. The rule applied by the British concerning the engagement of Tigers was that five Shermans were needed to destroy a single Tiger, but only one Sherman was to return from the engagement. [citation needed]