Complex sentence: From 20 September 1944 to 1 May 1945, the destroyer escort sailed with five convoys to British ports and upon cessation of hostilities in Europe she began preparations for Pacific duty.
Split into simpler sentences: From 20 September 1944 to 1 May 1945, the destroyer escort sailed with five convoys to British ports. Upon cessation of hostilities in Europe she began preparations for Pacific duty.