@PotomacBob
I have read, there are still cavalry units in the military - but they don't ride horses. What DO they do?
I was a US Army Cavalry Scout from the 1980's until 1992, when there were significant changes to the TO&E (Tables of Organization and Equipment) of the US Cavalry.
The MOS (Military Occupational Specialty) designation of US Army Cavalry is 19D (Nineteen Delta). {"Tankers" Armor Branch who crew M1A2 Abrams tanks are 19K (Kilo).} Until a few years ago the Armor branch, and the Cavalry were all trained at Fort Knox, Kentucky. Less than a decade ago they too are trained at Fort Benning (now Fort Moore), Georgia.
There are four major types of Cavalry units in the US Army.
1): Cavalry Scouts in the Scout Platoons of Infantry Battalions, and Armor (Tank) Battalions. From the 1960's into the early 1990's Mechanized formations (Tank or Mech Infantry) they had 6 M113 APCs (or some other vehicles such as the M114, or M109 ITV). Light Infantry, Airborne, etc. they usually used M151A2 quarter ton trucks ("Mutt" aka the modern Jeep); some units with "Jeeps" might have a dozen vehicles. Typically a Scout Platoon had 30-36 men led by a 1LT (First Lieutenant, who had some experience commanding a "Line" Platoon and on a Battalion Staff. Not always, sometimes we had a 2LT newly commissioned Second Lieutenant) {Because the Scout Platoon reported directly to the LTC (Lieutenant Colonel) commanding the Battalion; although the S2 Intelligence Officer (Staff Officer Two) often had taskings for the Scouts, and monitored our reports.)
1A): Starting in the late 1980's some Scout Platoons were mounted in 6 to 10 HMMWVs ("Humvees"). In the 1990's they began reducing Scout Platoons to just 18 Cavalry Troopers (including the Lieutenant) and mostly ceases conducting dismounted patrolling. {That is why I transferred to the Infantry that picked up the Dismounted Patrolling missions. Although Infantry units have always conducted dismounted patrolling.}
2): Divisional Cavalry Squadron a combined arms formation with 3 or 4 Cavalry Troops (Company sized with 3 to 5 Platoons), and a Tank Company, as well as organic Mortars (self-propelled, typically in a variant of an M113) and a Battery of Artillery. Reconnaissance was a secondary mission for the Divisional Cavalry Squadron. Screening (often a flank, but also a section of the Division Front to allow the rest of the combat forces to Mass to attack or defend). A Cavalry Squadron has the assets to simulate the presence of a combined arms Brigade; in particular to Soviet (or other threat) ground forces. Screening might also be between two US Army Divisions (or coalition forces). Screening would also include covering the movement of a Division (to prevent the enemy from observing AA ("Alpha-Alpha" Assembly Area) as the lead combat elements of a Division moves into a new area. Or screening a withdrawal or retreat.
Pursuit is another possible mission.
3): Cavalry Regiment similar to a Divisional Cavalry Squadron, but 3 to 4 times larger. Typically each Corps has a Cavalry Regiment or Armored Cavalry Regiment. They perform similar missions as a Divisional Cavalry Squadron, but on a larger scale. An Armored Cavalry Regiment can simulate the forward elements of a Combined Arms Division.
3A): Since c.2000 the US Army has "Light" Cavalry Squadrons and "Light" Cavalry Regiments mounted on Stryker 8-wheeled armored vehicles. They typically operate in conjunction with Airborne, Air Assault, and similar forces. Or as part of "Peace Keeping" forces.
4): Air Cavalry in the Vietnam era through the 1970's most of the "Air Cavalry" were Light Infantry transported by Helicopters. The US 11th Airborne Division was used for experiments in "Vertical Envelopment" aka using Helicopters to deploy Infantry to a location the enemy (hopefully) didn't expect. Just before deploying to Vietnam in 1965 the 11th Airborne was reflagged as the 1st Cavalry Division. In the 1970's the US 101st Airborne Division (Air Assault) became the only Division sized Air Mobile (by Helicopter) in the US Army, and the world (no other nation has such a large helicopter mobile unit). Several US Army Divisions have "Air Assault" Battalions or Brigades. {In World War Two the 1st Cavalry Division had Cavalry Branch troopers, but fought as the only 4 Regiment Division, but was effectively just a somewhat odd infantry division. In Vietnam the 1st Cavalry Division was just an honorific; only the Scout Platoons had Cavalry Troopers.)
4A): Air Cavalry a mix of Attack Helicopters (AH-1 "Cobra" or AH-64 "Apache") and Recon Helicopters (OH-58 "Kiowa" or OH-5 "Cayuse") and some other helicopters for service and support duties. In Vietnam, and until 1983 or 84 some Air Cavalry Squadrons had a small number of Cavalry Troopers who would deploy on UH-1 "Huey" (proper designation "Iroquois") to conduct reconnaissance duties on the ground in support of the unit mission. In the mid-80's the Air Cav focused upon the arial missions and greater "agility" and increasing firepower. Dismounts from Scout Platoons, the Cavalry Squadron, or an Infantry Battalion may be inserted by helicopter for certain missions.