Complex sentence: He was born at Bavaria in 1880 and entered the Army in 1898 as a cadet, in 1900 he was promoted to Leutant and in 1913 he join the general staff as a Hauptman, he served as a staff officer in the First World War.
Split into simpler sentences: He was born at Bavaria in 1880 and entered the Army in 1898 as a cadet. He served as a staff officer in the First World War.