Rumsfeld Answers Critics: In his first four months at the Pentagon, Defense Secretary Donald H. Rumsfeld has launched a score of secretive studies and posed hundreds of tough questions as he has tried to create a new vision for the American military, looking at everything from missile defenses and global strategy to the flaws of a Truman-vintage personnel system. Yet, in that short span, he has also rallied an unlikely collection of critics, ranging from conservative members of Congress and his predecessor as defense secretary to some of the generals who work for him.