https://en.wikipedia.org/wiki/Polish%E2%80%93Lithuanian_Commonwealth
https://www.britannica.com/place/East-Prussia
https://weaponsandwarfare.com/2020/03/15/poland-pre-wwii/
https://en.wikipedia.org/wiki/East_Prussia
https://en.wikipedia.org/wiki/History_of_Poland_(1918%E2%80%931939)
https://en.wikipedia.org/wiki/Polish%E2%80%93Lithuanian_War
https://ru.usembassy.gov/world-war-ii-allies-u-s-lend-lease-to-the-soviet-union-1941-1945/