Complex sentence: All of Pratt's wartime promotions expired by September 8, returning him to his permanent establishment rank of captain, and he entered the course of study for junior officers at the General Staff School in Washington, D.C. on September 1.
Split into simpler sentences: All of Pratt's wartime promotions expired by September 8, returning him to his permanent establishment rank of captain. He entered the course of study for junior officers at the General Staff School in Washington, D.C. on September 1.