With a jovial exchange of greetings and the signing of a wide-ranging arms control agreement, the United States and the Soviet Union appeared to reach an unparalleled level of trust and understanding in the winter of 1987.

But while the Intermediate-Range Nuclear Forces (INF) Treaty represented a milestone, it was not the finish line for the two superpowers. And while President Ronald Reagan and Soviet leader Mikhail Gorbachev appeared to hit it off, Reagan would dust off an old Russian proverb to characterize whatever faith he had in his adversary: “Trust — but verify.”

Each side has threatened to junk the treaty almost from its inception. Even before it was signed, conservative Washington Post columnist Charles Krauthammer was calling the pact lopsidedly unfair at best, dangerously unrealistic at worst.

Russian President Vladimir Putin, believing U.S. missile-defense plans constituted a violation of the treaty, talked about walking away from it a decade before President Trump brought the subject up.

The other problem Putin cited, however, is a shortcoming of the INF Treaty on which the Americans and the Russians can agree: As Post national security columnist Max Boot recently detailed, it does not govern emerging nuclear powers in the world, such as China, North Korea or Iran. As The Post’s Paul Sonne has reported, China in particular is rolling out new threats which, under the terms of the 31-year-old treaty, the United States cannot counter.

And so the treaty may go away. But a look back at the circumstances that brought the world’s most powerful enemies to the INF negotiating table in the first place may serve as a reminder that daunting, complicated geopolitical standoffs have been solved before.