You are entitled to your own opinion, but not to your own facts.
The fact is that the USSR and Germany signed a non-aggression pact, not a treaty of alliance. You can read the text [0] yourself and see that there is nothing resembling a war alliance.
Oh, the start of the war was awful in so many aspects, there were no rights. Second Polish Republic was aggressive state [1], [2]. It partitioned Czechoslovakia with Germany and Hungary in 1938. Soviets border on Poland lies about what was defined in Treaty of Versailles [3]. It does not excuse anything just show mixed things were. Have no idea about other parts of the German Soviet border [4].
The fact is that the USSR and Germany signed a non-aggression pact, not a treaty of alliance. You can read the text [0] yourself and see that there is nothing resembling a war alliance.
[0] https://en.wikisource.org/wiki/Molotov%E2%80%93Ribbentrop_Pa...