Victory Day (Zafer Bayramı) on August 30 is a national holiday in Turkey to commemorate the victory in the Battle of Dumlupınar against the Greeks, one of the final battles and the most decisive one in the Turkish War of Independence in 1922.
Turks often rewrite history to make their battles noble and justified, and the commemoration of Victory Day is no exception. According to the Turks, Greeks were invaders of Turkey and occupied Turkish land, which is why they were expelled in 1922. More accurately, this battle was meant to be a Greek War of Independence after being occupied by the Ottomans for hundreds of years.
For a Turkish take on this celebration, read "Turkey Recognizes Victory Day Aug. 30".
For a general history of the Battle of Dumlupınar, read here. This battle marked the beginning of the end of the Greek presence in Anatolia.
2012 marks the 90th Victory Day in Turkey.