Air assault
Organization and employment: Air assault and air mobility are related concepts. However, air assault is distinctly a combat insertion rather than transportation to an area in the vicinity of combat.
Air assault units can vary in organization; using helicopters not only in transport but also as close air fire support, medical evacuation helicopters and resupply missions. Airmobile artillery is often assigned to air assault deployments. Units vary in size, but are typically company to
brigade sized units.
Airmobile units are designed and trained for air insertion and vertical envelopment ("a maneuver in which troops, either air-dropped or air-landed, attack the rear and flanks of a force, in effect cutting off or encircling the force", air resupply, and if necessary air extraction.
One specific type of air assault unit is the US Army air cavalry. It differs from regular air assault units only in fulfilling a traditional cavalry reconnaissance and short raids role. Britain's 16 Air Assault Brigade was formed in 1999 following an amalgamation of elements of 5th Infantry Brigade (5 Airborne Brigade) and 24 Airmobile Brigade, bringing together the agility and reach of airborne forces with the potency of the attack helicopter. Similarly, the US 101st Airborne Division was originally classed as airborne, then airmobile and now air assault.

History: Air mobility has been a key concept in offensive operations since the 1930s. Initial approaches to air mobility focused on parachutists and the use of military gliders. During World War II many assaults were done by military gliders. The World War Two era German Fallschirmjäger, Brandenburgers, and the 22nd Air Landing Division glider borne paras laid the foundation for modern day air assault operations. In 1941 the U.S. Army quickly adopted this concept of offensive operations initially utilizing wooden gliders before the development of helicopters. Following the war, faster aircraft led to the abandonment of the flimsy wooden gliders with the then new helicopters taking their place. Four YR-4B helicopters saw limited service in the China Burma India theatre with the 1st Air Commando Group
In 1943 the Germans conducted the Gran Sasso raid which implemented many aspects of the air assault concept. Another example was the German Brandenburgers' glider borne operation at Ypenburg during World War Two.
In 1946, U.S. Marine General Roy S. Geiger observed the atomic bomb tests at Bikini Atoll and instantly recognized that atomic bombs could render amphibious landings difficult because of the dense concentrations of troops, ships and material at beachheads. During this time, The Commandant of the Marine Corps, Alexander Vandegrift, convened a special board known as the Hogaboom Board. This board recommended that the USMC develop transport helicopters in order to allow a diffused attack on enemy shores. It also recommended that the USMC form an experimental helicopter squadron. HMX-1 was commissioned in 1947 with Sikorsky HO3S-1s. In 1948 the Marine Corps Schools came out with Amphibious Operations—Employment of Helicopters (Tentative), or Phib-31, which was the first US manual for helicopter airmobile operations. The Marines used the term vertical envelopment instead of air mobility or air assault. HMX-1 performed its first vertical envelopment from the deck of an aircraft carrier in an exercise in 1949.
American forces later used helicopters for support and transport to great effect during the Korean War showing that the helicopter could be a versatile and powerful military tool.

First helicopter air assaults: The first helicopter airlift and helicopter sling load mission was conducted on September 13, 1951, during the Korean War. "Operation Windmill I" was conducted by the United States Marine Corps in support of a battalion clearing the enemy from a series of ridges around a basin called "The Punchbowl." In total seven HRS-1 Marine helicopters made 28 flights that delivered 8,550 kg (18,848 pounds) of supplies and evacuated 74 seriously wounded men.

On November 5, 1956, the Royal Marines' 45 Commando performed the world's first combat helicopter insertion with air assault during an amphibious landing as part of Operation Musketeer, in Suez, Egypt. 650 marines and 23 tons of equipment were flown in ten Westland Whirlwind Mark 2s of 845 Naval Air Squadron from the deck of HMS Theseus, and six each Whirlwinds and Bristol Sycamore HC.12s and HC.14s off HMS Ocean's embarked Joint Experimental Helicopter Unit (JEHU) (Royal Air Force). The plan was to use the helicopters to drop No. 45 Commando at Raswa, to the south of Port Said, in order to secure two vital bridges. Last-minute concerns about their vulnerability to ground fire meant that they were replaced in this role by French paratroops who conducted a daring low-level drop on 5 November, securing one of the two bridges intact. Instead No. 45 Commando was landed the following day, disembarking close to the seafront in the aftermath of the seaborne landing that had secured the area. This first-ever operational use of helicopters to land troops during an amphibious assault proved successful. With their carriers lying nine miles offshore, the marines were landed far more quickly than could have been achieved using landing craft, and without the need to get their boots wet. However ... they landed the marines in much the same place that old style landing craft would have put them.
In 1956, the United States Marine Corps executed the first Division-strength exercise of vertical envelopment when the 1st Marine Division was helicopter-lifted from converted WWII jeep carriers to landing sites at Camp Pendleton, CA, U.S. Marine Corps Base. One of the ships utilized for this exercise was the USS Thetis Bay. This exercise was the culmination of the Marines' developing strategy of vertical envelopment rather than amphibious assaults on heavily defended beaches. The maneuvers were well-covered by the media of the time, including LIFE Magazine. The Marine Corps subsequently adopted this method as standard operating procedure after proving that helicopters could be used to transport very large numbers of troops and large amounts of supplies in a timely fashion.
Operation Deep Water was a 1957 NATO naval exercise held in the Mediterranean Sea that involved the first units of the United States Marine Corps to participate in a helicopter-borne vertical envelopment operation during an overseas deployment.
During the Vietnam war the U.S. Army's 1st Cavalry Division conducted the first large scale air assault operation in combat during the Battle of Ia Drang.

Algerian War: The use of armed helicopters coupled with helicopter transport during the Algerian War for the French Army to drop troops into enemy territory gave birth to the tactics of airmobile warfare that continues today.
The machines of the French Army Light Aviation carried out a considerable number of missions against Algerian insurgents between 1955, when the Groupe d’Hélicoptères No.2 (GH 2) was created, and 1962 when the French empire in Algeria finally came to an end. GH 2 was based at Sétif – Aïn Arnat in the east of the country, and it was equipped primarily with machines to undertake transport missions, though the Vertol H-21C, would soon join the unit owing to concerns about the lack of machines which could both defend themselves and carry out offensive missions against the insurgents. Acquiring these machines lay in the hands of the licensee Piasecki given France's urgent need to have them on account of the circumstances. Usually, the H-21 could carry up to 18 troops, yet local operating (as well as climatic) conditions decreed that the French army examples could carry only up to around 12 troops each. In two years, GH 2 received the vast majority of the H-21s acquired by ALAT, which consisted of five squadrons by the end of 1958. A sixth squadron from the French naval air arm, the Aéronautique navale, had operated with GH 2 for little more than a year.
From 1955 to 1962, GH 2 took part in the major battles, which occurred near the frontier between Algeria and Tunisia, including the battle of Souk-Ahras in April 1958. The helicopters, including types such as the H-21, the Alouette II, the Sikorsky H-19 and Sikorsky H-34, together aggregated over 190,000 flying hours in Algeria (over 87,000 for the H-21 alone) and helped to evacuate over 20,000 French combatants from the combat area, including nearly 2,200 at night. By the time the war in Algeria had ended, eight officers and 23 non-commissioned officers from ALAT had died in the course of their duties.

Vietnam War: U.S. Army CH-21 helicopter transports arrived in South Vietnam on 11 December 1961. Air assault operations using Army of the Republic of Vietnam (ARVN) troops began 12 days later in Operation Chopper. These were very successful at first but the Viet Cong (VC) began developing counter helicopter techniques, and at the Battle of Ap Bac in January 1963, 13 of 15 helicopters were hit and four shot down. The Army began adding machine guns and rockets to their smaller helicopters and developed the first purpose built gunship with the M-6E3 armament system.
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