A radar-avoiding U.S. B-2 bomber dropped two earth-shattering 4,600-pound 'bunker-buster' bombs on Friday on a major link in Iraq's communications network in downtown Baghdad, defense officials said. It was believed to be the first use of the big bombs on Baghdad. Allied jets have pounded targets in the Iraqi capital with hundreds of bombs and missiles in the week-old war to depose President Saddam Hussein.