Poland was a nation-state on the European continent on Earth. Warsaw was the capital and largest city in Poland. People or things from Poland were generally described as Polish.
World War II started on 1 September 1939 when Germany invaded Poland.
23rd century Starfleet officer and USS Excelsior chief engineer Deniece Maliszewski was of Polish descent (Orion Press), as was 24th century Starfleet engineer Mikael Czawlytko. (Star Trek: Pendragon)
Future USS Alexandria-A counselor Christine Nycz was born in Warsaw in 2349. (Star Trek: Odyssey)