Complex sentence: In time he was promoted to Lieutenant colonel; (pol.Podpułkownik) and served in various offices and departments, eventually in 1951 ending up in the 10th Department, where he was one of the leading officers.
Split into simpler sentences: In time he was promoted to Lieutenant colonel; (pol.Podpułkownik). Pod he served in various offices and departments, eventually in 1951 ending up in the 10th Department, where he was one of the leading officers.