"I'd rather use the nuclear bomb," Nixon told Kissinger, his national security adviser, a few weeks before he ordered a major escalation of the Vietnam War."That, I think, would just be too much," Kissinger replied softly in his baritone voice, in a conversation uncovered among 500 hours of Nixon tapes released Thursday.Nixon responded matter-of-factly. "The nuclear bomb. Does that bother you?" he asked. Then he closed the subject by telling Kissinger: "I just want you to think big."He also said "I don't give a damn" about civilians killed by U.S. bombing.