Bill Bland: The German-Soviet Non-Aggression Pact of 1939

I found this to be a good, short primer on the Molotov-Ribbentrop Pact. It goes into detail on how the Soviets tried to pursue collective security with the British and French, only to have them both drag their heels until it was clear to the Soviets that they had no interest in actually agreeing to collective security. Even after the Soviets telegraphed that they would instead work with the Germans if the British and French didn’t get serious, they still wouldn’t.