Complex sentence: He subsequently became a lieutenant on 24 August 1821, a captain on 23 October 1824, a major on 5 June 1827 and a lieutenant-colonel on 8 September 1831.
Split into simpler sentences: He subsequently became a lieutenant on 24 August 1821, and captain on 23 October 1824. He became a major on 5 June 1827 and a lieutenant-colonel on 8 September 1831.