Complex sentence: He served in World War I as a "Fähnrich" (ensign) for these services he received the Iron Cross 2nd Class and was was promoted to "Leutnant" (second lieutenant) in 1919.
Split into simpler sentences: He served in World War I as a "Fähnrich" (ensign). For these services he received the Iron Cross 2nd Class and was was promoted to "Leutnant" (second lieutenant) in 1919.