I see you dropped a nuclear warhead on us, so now we'll return the favour - okay then we'll bomb someone else, how about that?

Cristina Hansell, a scholar at California's Martin Center for Nonproliferation Studies, figures the Ph.D. detectives might finger an alleged culprit — a surreptitious North Korean bomb, a stolen Russian device, a Pakistani weapon in extremists' hands — "with 65 to 70 percent likelihood."

"Are you going to bomb someone else on that basis?" she wondered.

SHOOT: Say a nuclear warhead is detonated on US soil and is traced to North Korea, what happens then? Lob a nuclear weapon at them, lob ordinary missiles? They then lob a nuke at Seoul with 30 million people right on their border. It gets ugly.

clipped from news.yahoo.com VIENNA – If the unthinkable happened, would we be left on the day after, as radioactive dust settled, with the unknowable? If a terrorist nuclear bomb destroyed the heart of a great city, how would we know who did it, with what? Mideast fanatics with a device improvised from stolen uranium? A weapon smuggled in by a rogue regime? A hijacked U.S. bomb? Where do you strike back? How do you head off another attack? President Barack Obama calls nuclear terrorism "the most immediate and extreme threat to global security." It's an unthinkable that's being thought about daily in classified corners of world capitals. But knowledgeable scientists and the investigators behind a new U.S. government report say the American nuclear establishment needs more specialists and more background data on possible bomb sources to do the detective job that awaits on that day after. "Al-Qaida has said it would if it could," he said.