Were Iran to acquire nuclear weapons, there is a grave risk it would be tempted to provide them to terrorists. After all, mass casualty terrorism done by proxies has worked well for Iran to date. The fear about what Iran might do with nuclear weapons is fed by the concern that Tehran has no clear reason to be pursuing nuclear weapons. The strategic rationale for Iran's nuclear program is by no means obvious. Unlike proliferators such as Israel or Pakistan, Iran faces no historic enemy who would welcome an opportunity to wipe the state off the face of the earth. Iran is encircled by troubled neighbors, but nuclear weapons does nothing to help counter the threats that could come from state collapse in Afghanistan, Pakistan, Iraq, or Azerbaijan. Achieving trans-Atlantic consensus on how to respond to Iran's nuclear program will be difficult. This is a remarkably bad time for the international community to face the Iran nuclear problem, because the tensions about the Iraq WMD issue still poison relations and weaken U.S. ability to respond. Nevertheless, Iran's nuclear program poses a stark challenge to the international nonproliferation regime. There is no doubt that Iran is developing worrisome capabilities. If the world community led by Western countries is unable to prevent Iranian proliferation, then it is unclear that there is much meaning to global nonproliferation norms.