During the 1980s - 1990s America had so many subs (39), that Russia's nationwide ABM system just couldn't handle them all.(intercept all their missile warheads). So the Kremlin wanted to turn to its back up "weapon", namely DISARMAMENT agreements. The Kremlin wanted to get America to cut way back on its subs, cutting them from 39 all the way down to just 12.

During the 1980s - 1990s America had so many subs (39), that Russia's nationwide ABM system just couldn't handle them all.(intercept all their missile warheads).

So the Kremlin wanted to turn to its back up "weapon", namely DISARMAMENT agreements.
The Kremlin wanted to get America to cut way back on its subs, cutting them from 39 all the way down to just 12.That way Russia's ABM system would be adequate for shooting down the missile warheads- because there would be fewer of them.
But America could hardly be expected to drastically disarm while the Cold War was raging !!
Solution: END THE COLD WAR, STUPID.
So that's what Russia did.
That disarmament was the motivation for Russia's peace-making is shown by what has happened since the end of the Cold War -- America has disarmed precipitously !!
Gorbachev's bold gamble has paid off (and will really pay off even more when war comes).
Bible Prophecy predicted Gorbachev's coming 2600 years ago with these words,