In the British Army

British Army

The British Army is the land warfare branch of Her Majesty's Armed Forces in the United Kingdom. It came into being with the unification of the Kingdom of England and Scotland into the Kingdom of Great Britain in 1707. The new British Army incorporated Regiments that had already existed in England...

, the Troop Sergeant Major (TSM) is the senior NCO

Non-commissioned officer

A non-commissioned officer , called a sub-officer in some countries, is a military officer who has not been given a commission...

 in a Royal Artillery

Royal Artillery

The Royal Regiment of Artillery, commonly referred to as the Royal Artillery , is the artillery arm of the British Army. Despite its name, it comprises a number of regiments.-History:...

 troop

Troop

A troop is a military unit, originally a small force of cavalry, subordinate to a squadron and headed by the troop leader. In many armies a troop is the equivalent unit to the infantry section or platoon...

, usually a Warrant Officer

Warrant Officer

A warrant officer is an officer in a military organization who is designated an officer by a warrant, as distinguished from a commissioned officer who is designated an officer by a commission, or from non-commissioned officer who is designated an officer by virtue of seniority.The rank was first...

 Class 2.

This differs from a cavalry

Cavalry

Cavalry or horsemen were soldiers or warriors who fought mounted on horseback. Cavalry were historically the third oldest and the most mobile of the combat arms...

 troop or infantry

Infantry

Infantrymen are soldiers who are specifically trained for the role of fighting on foot to engage the enemy face to face and have historically borne the brunt of the casualties of combat in wars. As the oldest branch of combat arms, they are the backbone of armies...

 platoon

Platoon

A platoon is a military unit typically composed of two to four sections or squads and containing 16 to 50 soldiers. Platoons are organized into a company, which typically consists of three, four or five platoons. A platoon is typically the smallest military unit led by a commissioned officer—the...

, in which the highest-ranking NCO is usually a sergeant

Sergeant

Sergeant is a rank used in some form by most militaries, police forces, and other uniformed organizations around the world. Its origins are the Latin serviens, "one who serves", through the French term Sergent....

.

Troop Sergeants Major in the cavalry

The appointment was formerly current in British cavalry

Cavalry

Cavalry or horsemen were soldiers or warriors who fought mounted on horseback. Cavalry were historically the third oldest and the most mobile of the combat arms...

 units. It was introduced in 1813 to replace the Quartermaster

Quartermaster

Quartermaster refers to two different military occupations depending on if the assigned unit is land based or naval.In land armies, especially US units, it is a term referring to either an individual soldier or a unit who specializes in distributing supplies and provisions to troops. The senior...

 as the senior NCO of a troop, and was roughly equivalent to a Colour Sergeant

Colour Sergeant

Colour sergeant or colour serjeant is a non-commissioned title in the Royal Marines and infantry regiments of the British Army, ranking above sergeant and below warrant officer class 2....

 in the infantry. As the squadron replaced the troop as the main tactical and administrative division of the regiment

Regiment

A regiment is a major tactical military unit, composed of variable numbers of batteries, squadrons or battalions, commanded by a colonel or lieutenant colonel...

, so the Squadron Sergeant Major superseded the Troop Sergeant Major.

It was revived in 1938 as an appointment of the short-lived rank of Warrant Officer Class III (WOIII). The new Troop Sergeant Major, and his infantry counterpart, the Platoon Sergeant Major

Platoon Sergeant Major

Platoon Sergeant Major was an appointment in the British Army in the short-lived rank of Warrant Officer Class III , created in 1938. The Platoon Sergeant Major, and his cavalry counterpart, the Troop Sergeant Major, were part of an experiment in giving experienced NCOs command of units formerly...

, were part of an experiment in giving experienced NCOs command of units formerly reserved for commissioned officers (troops and platoons). The experiment was not considered a success, and no promotions were made to the rank after 1940: most existing WOIIIs were commissioned as lieutenants.

The old appointment is presumably why Staff Sergeant

Staff Sergeant

Staff sergeant is a rank of non-commissioned officer used in several countries.The origin of the name is that they were part of the staff of a British army regiment and paid at that level rather than as a member of a battalion or company.-Australia:...

s are referred to and addressed as "Sergeant Major" in British cavalry regiment

Regiment

A regiment is a major tactical military unit, composed of variable numbers of batteries, squadrons or battalions, commanded by a colonel or lieutenant colonel...

s. A Staff Sergeant can command a cavalry troop, in the same way as the old WOIII TSMs.