As for nuclear weapons, Beijing possesses far fewer than Russia and America. Noted the Union of Concerned Scientists: “The small size and limited capabilities of China’s nuclear arsenal make the threat of a first use of nuclear weapons against the United States or Russia highly unlikely and not at all credible, since it would invite massive nuclear retaliation as well as international condemnation.”

So far, at least, the fears which motivated proposals for preventive war have proved false. It is impossible to know how U.S. military strikes would have played out, but they would have been a dangerous experiment best not conducted.

Of course, the fact that restraint toward Beijing was the best course does not necessarily mean Washington should accept a nuclear North Korea. Nevertheless, the case of China demonstrates the virtue of caution, inherent limitations on intelligence, inevitable uncertainties about consequences, and imperative of carefully counting the cost of military action, no matter how the summit turns out.

No one wants a nuclear North Korea. But it is not the only threatening, even scary regime that has acquired nuclear weapons. Also, Pyongyang is not the only case in which Washington has considered war to disarm such a country. Launching preventive strikes on the North might tempt some people, but history argues against loosing the dogs of war. While we don’t know what war with Pyongyang would bring, we do know the horrors that wars usually yield.

Doug Bandow is a senior fellow at the Cato Institute. A former special assistant to President Ronald Reagan, he is author of Tripwire: Korea and U.S. Foreign Policy in a Changed World and coauthor of The Korean Conundrum: America’s Troubled Relations with North and South Korea.

Image: Missiles are driven past the stand with North Korean leader Kim Jong Un and other high ranking officials during a military parade marking the 105th birth anniversary of the country's founding father, Kim Il Sung in Pyongyang, April 15, 2017. REUTERS/Damir Sagolj