“Together, they could lead the world” to peace, he told the reporter, and he sang a song after the interview.

Putin and Trump have called for stronger nuclear weapons in their countries since then. Now Gorbachev is back in the media — warning of possible global war.

“The world today is overwhelmed with problems,” he wrote in the first line of his essay. “Policymakers seem to be confused and at a loss.”

He listed some problems: “the militarization of politics and the new arms races,” bellicose world leaders and a media that echoes them. Tanks and weapons in Europe — “placed closer to each other, as if to shoot point-blank.”

“It all look as if the world is preparing for war,” Gorbachev wrote.

His tone had darkened since his song in December — if not since the Soviet Union dissolved beneath his feet a quarter-century ago. But Gorbachev's advice for the world was much the same: Do like he and former president Ronald Reagan — whose cooperation and mutual disarmament may well have averted World War III.

Gorbachev's essay summarizes the lurching end of the Cold War in a few brief lines: “In the second half of the 1980s, together with the U.S., we launched a process of reducing nuclear weapons and lowering the nuclear threat.”

The reality wasn't so neat, though it seemed impossibly rapid to a world that had spent a century under the cloud of global war.

Former Soviet president Mikhail Gorbachev looks through a book about his late wife, Raisa Gorbachev, in Moscow. (Ivan Sekretarev/Associated Press)

Gorbachev took over the Communist Party in 1985, as Reagan was beginning his second term in the White House with pushes for a new nuclear missile and a more robust military.

Many Americans credit Reagan's hard line on military policy — like his push for missile defense — with forcing the Soviet Union to reform and eventually collapse.

In his own interviews, Gorbachev has spun history differently.

“Our interests coincided,” he told The Washington Post in 2004, after giving Reagan's coffin a fond pat at his funeral.

“We both knew what kind of weapons we each had,” he said. “There were mountains of nuclear weapons. A war could start not because of a political decision, but just because of some technical failure.”

Whatever inspired him, Gorbachev is remembered for softening a totalitarian empire — making the Soviet Union more open and liberal while cutting its nuclear stockpiles, as Reagan reciprocated.

The push for world peace was distilled in Reagan's famous call in 1987 — “Mr. Gorbachev, tear down this wall!" — followed two years later by the border opening between East and West Germany, and the destruction of the Berlin Wall.

Gorbachev would later complain that the peacemaking got out of hand — after his rivals took advantage to oust him in a coup d'état, which led to his resignation on the same day the Soviet flag fell at the Kremlin.

Now, as he sees signs of peace undone across the world, he is calling on the Kremlin and White House's new occupants to join forces again and stop it.

In Time, Gorbachev urged “the presidents of two nations that hold over 90 percent of the world's nuclear arsenals” to push for a U.N. resolution condemning nuclear war.

But neither Trump nor Putin sound like they want his advice.

“The United States must greatly strengthen and expand its nuclear capability,” Trump wrote in a tweet on Dec. 22 — the week of the anniversary of Gorbachev's resignation.