A semi-vanquished enemy is rising zombielike from the crypt of America’s dimly remembered wars. North Korea is gleefully shooting missiles over Japan and splashing them into the Pacific Ocean. With astounding technical felicity, it is building a weapons system that may soon be able to hoist hydrogen bombs into Los Angeles, Chicago or even Manhattan. Meanwhile, two neophyte leaders with strange hair and thin skins are insulting each other in bizarre ways. President Trump called Kim Jong-un “Rocket Man” and threatens to “totally destroy North Korea.” Mr. Kim called Mr. Trump “a mentally deranged U.S. dotard” and threatens to “definitely tame” him with “fire.”

One of them, at least, should know better.

With a quiver of nuclear-tipped intercontinental missiles, the North Korean leader seems to have a good shot at doing what his father and grandfather did — living despotically to a ripe old age and dying from natural causes. Yet deep in his dictatorial DNA, Kim Jong-un surely knows the risk of provoking a full-scale war with the United States. It did not go well for his family the last time around. During the Korean War (1950-53), his grandfather — Great Leader Kim Il-sung — cowered in bunkers as American bombs flattened his cities and legions of his people died.

What this should teach American policy makers — especially our history-challenged president and his blood-and-soil backers — is that a North Korean offensive strike is unlikely. That is, unless the Kim regime is provoked, perhaps by a particularly warmongering early-morning tweet, into believing that its existence really is at risk. The Trump administration needs to keep Kim family history in mind. It is a criminal enterprise focused on long-term survival, far more adept at enslaving its people than fighting big-boy wars.

Sadly, the United States has largely forgotten the lessons of the Korean War, even though that conflict cost the lives of more than 33,000 American combatants. The causes of this collective amnesia are varied: The Korean War ended in an inglorious tie that was impossible to celebrate. It produced no Greatest Generation myths and few memorable movies. Then came Vietnam — the first war to be truly televised, a war that is still being parsed on public television. Vietnam seared itself into our literary and cinematic culture, blotting out Korea, the Forgotten War.