Complex sentence: Many vessels from Hellyer's North Sea fleet were lost during the war, and after the war they decided to concentrate on the distant fishing grounds off the coast of Iceland and the Barents Sea, selling off the remaining North Sea trawlers.
Split into simpler sentences: Many vessels from Hellyer's North Sea fleet were lost during the war. After the war Hellyer's decided to concentrate on the distant fishing grounds off the coast of Iceland and the Barents Sea, selling off the remaining North Sea trawlers.