History lessons sometimes need to be delivered on the fly.

Donald John Trump said recently that U.S.-Russia relations are at their “worst” in the history of the two nations. Tensions are rising over the Russian involvement in the Syrian civil war. The president wants relations to improve. Indeed, he still cannot bring himself to say out loud that the Russians are complicit in Syria’s use of chemical weapons against Syrian civilians.

Are bilateral relations the worst ever?

Ohhh, no. Not even close.

Let’s flash back about, let’s see, nearly 55 years.

Russia was known as the Soviet Union back then. The communists ran the government. Vladimir Putin would become head of the commies’ spy agency, the KGB.

What did the communists do to bring U.S.-Soviet relations to their nadir? They began installing offensive missiles in Cuba, capable of hitting targets throughout the Western Hemisphere with nuclear weapons.

Thus, the Cuban Missile Crisis was born.

President Kennedy got word of the intelligence. He summoned his National Security Council to the White House. He heard suggestions from his national security brass ranging from invading Cuba, bombing the missile sites, leveling economic sanctions, none of the above, all of the above.

The president settled on a naval blockade and an ultimatum: He told Soviet leader Nikita Khrushchev to remove the missiles or else. He went on national TV and told the nation — and the world — that any attack from Cuba against any target in this hemisphere would be seen as an attack on the United States and would produce a “full retaliatory response” from this country against the Soviets.

The commies blinked. They took down the missiles in exchange for our taking down of missiles in Turkey.

Crisis averted — along with a nuclear holocaust.

That qualifies as the worst, Mr. Trump.