Complex sentence: Londonderry Port and the docks at Lisahally played a vital part for the Allies in World War II during the war's longest running campaign, the Battle of the Atlantic which eventually saw the surrender of the German U-Boat fleet at Lisahally on 8 May 1945.
Split into simpler sentences: Londonderry Port and the docks at Lisahally gave vital service to the Allies in the longest running campaign of World War II, the Battle of the Atlantic. This ended with the surrender of the German U-Boat fleet at Lisahally on 8 May 1945.