Maxwell was again selected for officer training, and on 5 July, he was posted to No. 6 Officers' Cadet Battalion. He was promoted to company sergeant major on 7 August, before rejoining the 18th Battalion on 11 September. Nine days later, he was engaged in action near Westhoek during the Third Battle of Ypres when he performed the deeds that earned him the Distinguished Conduct Medal. In the battle, the commander of a platoon was killed; Maxwell took command and led it into attack. Noticing that one of the newly captured positions was under heavy fire, Maxwell dashed to it and led the men to a safer and more tactically secure position, thus minimizing casualties.