Complex sentence: He then took command of the 61st (2nd South Midland) Division in May 1916 and was engaged in the disastrous diversionary battle for the Somme offensive at Fromelles on 19th July 1916.
Split into simpler sentences: He then took command of the 61st (2nd South Midland) Division in May 1916. He was responsible for the disastrous diversionary battle for the Somme offensive at Fromelles on 19th July 1916.