Complex sentence: He was educated at Clifton College from May 1913 to July 1916, then trained as an officer at Wellington Cadet College in India, and commissioned as a second lieutenant on the Unattached List for the Indian Army on 18 June 1917.
Split into simpler sentences: He was educated at Clifton College from May 1913 to July 1916. He trained as an officer at Wellington Cadet College in India and was commissioned as a Second Lieutenant onto the Unattached List for the Indian Army 18 June 1917.