Indonesian Army Day, observed every December 15, commemorates the Battle of Ambarawa during the Indonesian War of Independence, where the Indonesian Army recaptured Ambarawa from Allied troops. This day honors the active and reserve personnel of the Indonesian Army, as well as army veterans, through military parades, ceremonies, and various events. The Indonesian Army, one of the three branches of the Indonesian National Armed Forces, was formed in response to the need for national defense following Indonesia's proclamation of independence in 1945. The battle itself began on November 23, 1945, and lasted until December 11, resulting in significant casualties for the Allies and marking a pivotal moment for Indonesian sovereignty. The anniversary of the final day of the battle, December 15, was subsequently declared Indonesian Army Day. This observance should not be confused with Indonesian Armed Forces Day, which is celebrated on October 5.