Complex sentence: The Second Battle of El Alamein marked a major turning point in the Western Desert Campaign of the Second World War that took place over 13 days from 23 October--4 November 1942.
Split into simpler sentences: The Second Battle of El Alamein marked a major turning point in the Western Desert Campaign of the Second World War. The battle took place over 13 days from 23 October--4 November 1942.