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].
[1] https://en.wikipedia.org/wiki/Polish%E2%80%93Czechoslovak_bo...
[2] https://en.wikipedia.org/wiki/Polish%E2%80%93Ukrainian_War
[3] https://en.wikipedia.org/wiki/Treaty_of_Versailles
[4] https://en.wikipedia.org/wiki/German%E2%80%93Soviet_Border_a...