the ndh army withdrew towards zagreb with german and cossak troops by early 1945, and continued fighting for a week after the german surrender on may 9th, 1945. they were soon overpowered and the independent state of croatia (ndh) effectively ceased to exist in may 1945, near the end of the war. the advance of tito's partisan forces, joined by the soviet red army, caused mass retreat of the ustaše towards austria.