Re: "the Army's top Sergeant Major"
Yep , one for each level of HQ. They are advisors to the Commander on matters enlisted, not shouty type SMs.
In Australia …
The RSM-A is responsible to the Chief of Army, but responsive to all ranks across Army. The RSM-A is a member of the personal staff of the Chief of Army. The RSM-A’s primary role is to represent to the Chief of Army, and others, the solicited and unsolicited views concerns and opinions of Soldiers in the Army, but also carry the Chief of Army’s message down and across the ranks.
Biting the hand that feeds IT
