Well if you want to go back we could start with 1945 and the Yalta agreement for the Allies to stop their advance at Berlin. The Russians did not.
As for missiles 15 minutes from Moscow, I lived with the 4 minute warning for years in the 60's and 70's from a country that did not keep it's side of the deal.
China was simply waiting until they could steal the military technology of the West and reverse engineer it to the point where they can now threaten their smaller neighbours
IG.