Complex sentence: He was born in Berlin and joined the army in October 1914 as an officer cadet and served World War I as a leutnant in an engineer battalion and as a commander of armoured trains.
Split into simpler sentences: He was born in Berlin and joined the army in October 1914 as an officer cadet. He served in World War I as a leutnant in an engineer battalion and as a commander of armoured trains.