“There was neither the will nor the mechanism to sustain disarmament and intrusive monitoring against Iraqi obstruction,” Charles Duelfer, the deputy director of the United Nations weapons-inspection group from 1993 until 2000, wrote in his detailed account of the negotiations, “Hide and Seek: The Search for Truth in Iraq.” The collapse of the U.N. effort to disarm Saddam Hussein’s regime contributed to the Bush Administration’s decision to invade Iraq, in 2003, even though the country no longer had weapons of mass destruction by then. But Iraq had lied so often about its past activities and its future intentions to rebuild that Baghdad and the United Nations had reached a dangerous deadlock.

The U.S. effort in North Korea faces similar challenges. “What if we believe North Korea has enough fissile material for thirty-five weapons and it only declares thirty?” Frank Aum, a former senior adviser on North Korea in the Office of the Secretary of Defense, who is now at the U.S. Institute of Peace, told me. “Will the Administration say, ‘That’s good enough,’ and declare victory?”