RSM Joseph Foy, D.C.M., from a group photo taken at Wolseley Barracks, London, Ontario. (circa 1922)
The Regimental Sergeant Major (R.S.M.) is the senior non-commissioned soldier in an infantry battalion. During the First World War, this appointment was held by the senior soldier at the rank of Warrant Officer, Class 1, and normally only one man on regimental duty held this rank. The term "Regimental Sergeant Major" itself starts to appear in contemporary documents such as individual service records about 1916.
The R.S.M. is the principal advisor to the Commanding Officer (C.O.) on matters of discipline, dress, deportment, and drill and ceremonial. He will also be relied upon for his experience to advise on methods and organization of training, and all manners of provision of support (personnel administration and logistics) within the battalion. The R.S.M. is the principal disciplinarian within the battalion for those matters which, because of their nature or severity, have not had to be referred for charges under the Kings Regulations and Orders.
While the C.O. will exercise command of the battalion through a chain-of-command consisting of the Company and Platoon Commanders, the R.S.M. has a parallel chain of communications through the Warrant Officers (i.e, the Company Sergeants Major) and the Sergeants within the Companies. This supplementary chain of communication ensures that the mood of the battalion and the complaints of the soldiers can be passed upward and eventually reach the C.O's. ear as needed to help maintain order and discipline within the battalion.
During the First World War, five men held the appointment of R.S.M. of The Royal Canadian Regiment:
See this excerpt from the Standing Orders of The Royal Canadian Regiment, published in 1935, for an overview of the duties of, and expectations placed upon, a Regimental Sergeant Major.