Poland does try though within months of becoming a nation again, annexing the Western Ukrainian People's Republic and laying claim to any land they once held or felt they should hold including chunks of Belarus, Ukraine, most of the Lithuanian-Beylarussian SSR (only a bit of Lithuania taken but should count as part of the annexation attempt and success of much of Belarus being occupied), and parts of Galacia, Carpathia, and Ruthenia claimed by Ukraine, local slavic ethnicities. though handed over by Romania and Hungary. Lithuania again when that was an independent state and the Soviet war was over. Annexing two territories and not being on official speaking terms till 1938 over the matter.
Czechoslovakia invaded them over border conflicts and was pretty clearly in the wrong, however then Poland did a non-aggression pact with Germany in '38 to take back all of Zaolzie and assist in the destruction of Czechoslovakia.
And Poland wasn't even independent when the century began, and was part of the Soviet bloc after WW2.
Poland does try though within months of becoming a nation again, annexing the Western Ukrainian People's Republic and laying claim to any land they once held or felt they should hold including chunks of Belarus, Ukraine, most of the Lithuanian-Beylarussian SSR (only a bit of Lithuania taken but should count as part of the annexation attempt and success of much of Belarus being occupied), and parts of Galacia, Carpathia, and Ruthenia claimed by Ukraine, local slavic ethnicities. though handed over by Romania and Hungary. Lithuania again when that was an independent state and the Soviet war was over. Annexing two territories and not being on official speaking terms till 1938 over the matter.
Czechoslovakia invaded them over border conflicts and was pretty clearly in the wrong, however then Poland did a non-aggression pact with Germany in '38 to take back all of Zaolzie and assist in the destruction of Czechoslovakia.