Following a heavy defeat for the Americans at the Battle of Sidi Bou Zid on 14 February, US troops were ordered to retreat from the east of the Atlas Mountains range to the west, where a defensive position would be more tenable. After receiving amendments to his plan of attack from the Italian military command, Field Marshall Rommel was ordered to launch an attack through the Kasserine and Sbiba passes, with assistance from General von Arnim, in an attempt to clear Allied forces from the mountains. Allied forces in Sbiba pass held out well against the German attack but the Allied forces holding Kasserine pass were pushed into retreat by a German advance on 19 February. The Allies held out a last ditch defence near the town of Thala and managed to stem the German advance. Heavy artillery bombardment and a lack of supplies forced Rommel to order a retreat on 23 February.