In a festively bedecked dining hall, US Defense Secretary Donald H. Rumsfeld served Christmas Eve dinner to dozens of US soldiers, then fed them his view, with a mix of optimism, caution and emotion, of why the war that has cost more than 2,150 US lives must be won. "We will win this war. It's a test of wills, and let there be no doubt that is what it is," he said. Rumsfeld told the troops that "generations before you have persevered and prevailed, and they too were engaged in a test of wills." "In this fight, the vast majority of Iraqis stand on the side of freedom," he said over the roar of helicopters flying over a regional US military headquarters that once was a palace of Saddam Hussein.