Complex sentence: Stockwell was stationed in India until 1929, he was promoted lieutenant on 1 February 1925, and then seconded to the Royal West African Frontier Force from 1 January 1930, he was promoted captain on 25 June 1932.
Split into simpler sentences: Stockwell was stationed in India until 1929, where he was promoted to lieutenant on 1 February 1925,. He as then seconded to the Royal West African Frontier Force from 1 January 1930, and promoted to captain on 25 June 1932.