If you are not familiar with recent Polish history during World War II and later, then watch this short video that explains it very well through great animations of Poland’s fight for freedom against the Germans and Soviets.
“Because we do not beg for freedom, we fight for it.”
– General Witold Urbanowicz / 303 Squadron commander
If you speak Polish, then there’s also a Polish version for you:
The film was made by the Institute of National Remembrance (Instytut Pamięci Narodowej), a Polish government agency.