After the dropping of the two A-Bombs on Japan, there was relief that the war was over. However, after several years, questions began to be asked as to the wisdom and morality of having used the atom bombs. Truman and his supporters justified his order to drop the bombs claiming it had actually been a humane act since millions of Japanese and Americans would have been killed if the United States had invaded Japan instead of dropping the bomb. Truman also answered critics who said that a demonstration should have taken place first. First, the US only had two bombs. If they announced to Japan that they were going to demonstrate the power of the bomb and the bomb did not work, it would have encouraged the Japanese to continue fighting. There was no guarantee that the bombs would work. Second, there was fear that if the US announced a demonstration, the Japanese might move American POWs to the site. The major argument however, continued to be that it saved many American lives.