Army leaders huddled in secret last week to contemplate one of the most consequential decisions in two generations: whether the time has come to replace the Abrams main battle tank and what exactly a fifth-generation combat vehicle replacement might be. On Feb. 24, the Army Requirements Oversight Council -- a body chaired by the service's chief of staff -- met to discuss a potential follow-on to the Abrams tank but did not reach a decision. “I can just assure you...