The National Independence Day, celebrated on November 11, is the most important event in modern Polish history. After 123 years of partition by Prussia, Austria, and Russia, First Marshal of Poland, Józef Piłsudski, led the fight for the independence at the end of the Word War I. Gaining the independence and restoring the nation was no small task. Poland was split between three, very different occupiers, with different infrastructure, governmental and judicial systems, languages, and levels of development.
After Bolshevik Russia attacked Poland in 1919 and suffered a great defeat in Battle of Warsaw in 1920, Second Polish Republic finally established it's right to exist as a strong nation. Until this day, Józef Piłsudski is recognized as the most important Polish statesman. You can find more information about the National Independence Day here.
During the World War II (1939-1945) , under the German occupation, and then under the communist rule (1945-1989) the National Independence Day on November 11th was forbidden. Currently, every year Polish statesmen gather at the Piłsudski Square for the change of guards at the Tomb of the Unknown Soldier and the arm forces defilade afterwards.