Well actually he's right (or arguably right) on this point. The text of the pact was that it's in force until April 1946, and there isn't an early "opt out" clause. The denunciation only meant that it wouldn't be in force after April of '46. (from your link) So the Soviets did break the pact by attacking before April '46. (Stalin - "So sue me" ) But back to the topic: Can you post the text of the "proposed surrender"? I doubt that it would agree to return all conquered territory, pay reparations, give up war criminals etc.