 In spite of this , three attempts during the winter of 1943 / 44 by Fifth Army to break through into the <unk> valley at Cassino failed . As spring approached in 1944 , Alexander concentrated his forces in great secrecy by thinning out the Adriatic front and bringing the bulk of Eighth Army 's striking power to the Cassino front . The combined attack of his two armies during the fourth and final Battle of Monte Cassino in early May took Kesselring by surprise and led to the Allied capture of Rome in early June . 
