Complex sentence: After brief duty in Hawaii, he studied at the U.S. Army Command and General Staff School at Fort Leavenworth, Kansas in 1928--29, and upon graduating served as an instructor in tactics at the U.S. Army Infantry School.
Split into simpler sentences: After brief duty in Hawaii, he studied at the U.S. Army Command and General Staff School at Fort Leavenworth, Kansas in 1928--29. Upon graduating from the U.S. Army Command and General Staff College at Leavenworth, he served as an instructor in tactics at the U.S. Army Infantry School.