September 9. September 9 is the 252nd day of the year (253rd in leap years) in the Gregorian calendar; 113 days remain until the end of the year. Events Pre-1600 337 ??? Constantine II, Constantius II, and Constans succeed their father Constantine I as co-emperors. The Roman Empire is divided between the three Augusti. 1000 ??? Battle of Svolder, Viking Age. 1141 ??? Yel?? Dashi, the Liao dynasty general who founded the Qara Khitai, defeats the Seljuq and Kara-Khanid forces at the Battle of Qatwan. 1320 ??? In the Battle of Saint George, the Byzantines under Andronikos Asen ambush and defeat the forces of the Principality of Achaea, securing possession of Arcadia. 1488 ??? Anne becomes sovereign Duchess of Brittany, becoming a central figure in the struggle for influence that leads to the union of Brittany and France. 1493 ??? Battle of Krbava Field, a decisive defeat...