Complex sentence: Demuth received a commission with the rank of lieutenant in the British Army on 23 October 1942 where he served in the Pioneer Corps, for whom he composed the Regimental march in 1943.
Split into simpler sentences: Demuth received a commission with the rank of lieutenant in the British Army on 23 October 1942. He served in the Pioneer Corps, for whom he composed the Regimental march in 1943.