Complex sentence: He was transferred to the 3rd Battalion, Grenadier Guards, on 14 August 1915 and assigned as a staff officer, but he requested to be returned to active duty with his battalion, a request granted before the Battle of the Somme.
Split into simpler sentences: He was transferred to the 3rd Battalion, Grenadier Guards, on 14 August 1915 and assigned as a staff officer. However, he requested to be returned to active duty with his battalion, a request granted before the Battle of the Somme.