Osama bin Laden thinks that acquiring nuclear weapons is a religious duty. He has been trying to get them since 1993. Were he to acquire a nuclear weapon and detonate it in, say, Times Square on a weekday, somewhere around a million people would die, and a huge chunk of Manhattan would be completely destroyed. It is hard to imagine a worse development in the War on Terror than bin Laden getting a nuclear weapon.
The good news is that George W. Bush recognizes the gravity of this threat. In December 2001, for instance, he called the possibility that terrorists might gain weapons of mass destruction “the great threat to civilization.” The bad news is that he has not acted on this recognition. He did, of course, invade Iraq, where it turned out that there were no weapons of mass destruction. But even before the invasion, when many people (myself included) believed that Iraq did have WMD, most people did not believe that Iraq had the most dangerous weapons of all: nuclear weapons. There were, however, many other ways in which we knew that terrorists might be able to obtain nuclear weapons and/or fissile material. It would seem obvious, after 9/11, that dealing with these ought to be among our top priorities. Oddly enough, however, they were not. And the result is that we are considerably less safe now than we might have been.
While there is a broad consensus that we need to try to block every step on the path terrorists would need to follow in order to acquire nuclear weapons, transport them to this country, and detonate them, the most difficult step on this path seems to be the acquisition of fissile materials — highly enriched uranium or plutonium. I will therefore focus on how we have tried to stop terrorists from getting these materials in several of the most important areas.