Well, let's ask like this: Why does the US have nukes? What country could invade them? Canada? MEXICO? Even the Chinese or Russians could be beaten easily in a war. The reason the nukes are there is because they don't want anyone to try. Deterrent, not actual weapon. As Pratchett put it, "Leonardo wanted to invent a weapon…
sundance: Well, the Nazis DID have loads of rocket scientists so they might have been able to build a rocket capable of flying to the moon if they persisted longer. Of course, they'd probably finish their nuke research first (well, before they get the moon-rockets, the US would probably have nukes first but would need to…