Defense Secretary Robert Gates is responsible for overseeing the U.S. wars in Afghanistan and Iraq, but on Thursday he took on a new war — on Capitol Hill, after a congressional panel added nearly a half-billion dollars to next year's defense budget for a jet engine the military insists it doesn't need. Gates called the move "a waste of money" and promised that the Pentagon "will strongly resist efforts to impose programs and changes on the Department that the military does not want, cannot afford, and that takes dollars from programs and endeavors the military services do need."

Gates' attack followed a decision by the House Armed Services Committee to add $485 million to next year's $726 billion defense budget (which includes $159 billion for the wars in Afghanistan and Iraq) to begin development of a second engine source for the Pentagon's single-engine F-35 fighter, the largest defense program in history. (See pictures of Robert Gates in Afghanistan.)

This is a serious showdown even for a man who has made challenging politicians and the military brass on unnecessary spending a hallmark of his tenure. Gates has already plucked the low-hanging fruit from the Pentagon money tree, ending production of the Air Force's F-22 fighter and the Army's Future Combat System last year. Both were seen by many as Cold War hangovers, giving even politicians cover for their termination. But now come tougher decisions.