By Korea, helicopters were more numerous but were still confined largely to support roles, primarily search and rescue and medical evacuation, not to combat. They were also used in certain logistical roles by both the U.S. Army and the Marine Corps. Although Army leaders thought about using helicopters to ferry troops during Korea, the service was prohibited from operating large aircraft by a law passed when the U.S. Air Force was created in 1947. The Army and the Air Force signed an agreement on November 4, 1952 that continued the limitation on the size of Army fixed-wing aircraft, but redefined helicopters by function performed in the combat zone. This paved the way for the use of large Army helicopters. This came too late to seriously impact the war, but the Army sent the 6^th Transportation Company (Helicopter) with Sikorski H-19s to Korea before the war ended.

The United States first used this new concept of warfare, soon named "air mobility" during the early years of its involvement in the Vietnam conflict. The Vietnam War was the first real helicopter war. The Army quickly began refining its way of fighting as the war escalated.

American H-21 helicopters were used to ferry Army of the Republic of Viet Nam (ARVN) troops into battle against communist Viet Cong guerrillas in 1962. At first, communist troops fled when the troop-carrying helicopters landed. But at the important battle of Ap Bac, they soon learned that if they stood their ground, they could bring down the helicopters with relative ease. Communist training manuals described the best ways to shoot at the H-21 and Huey helicopters—how to shoot ahead of the target to increase the chance of hitting it and where to shoot to cause the most damage.

Despite the proven vulnerability of helicopters to ground fire, the U.S. Army soon fully embraced the concept of "air mobility." By the mid-1960s, as American involvement in Vietnam dramatically increased, the Army began moving massive amounts of troops by air, not just the small groups of only a few years earlier. Some combat operations involved over 100 helicopters at a time, plus fixed-wing air support to drop bombs and fire rockets at enemy troops.

"Air mobility" came at a heavy price, however. During the Vietnam War, between 1962 and 1973, the United States lost 4,869 helicopters to all causes (with more than a thousand lost in 1968 and another thousand in 1969). Fifty-three percent of these losses were due to enemy fire (including enemy attacks on airbases). The rest resulted from operational accidents. The high rate of operational accidents occurred largely because helicopters are prone to mechanical breakdown if not regularly maintained, and during a war, maintenance often suffers. Vietnam's heavy jungle canopy also made helicopter operations difficult, with few places to land a stricken helicopter.

Once the United States had pioneered the use of helicopters in combat, other countries soon followed. None could create large "airborne cavalry" units like the U.S. Army, but many countries copied the concept of using helicopters to ferry troops into and out of combat areas quickly, particularly when fighting rebel groups. They often used U.S. helicopters for this purpose. Countries like Great Britain and the Soviet Union usually chose to move primarily elite troops by helicopter. U.S. Army airborne cavalry units like the famed 101^st Airborne and the 82^nd Airborne tended to be better trained than most cavalry units.

By the 1970s, as Vietnam came to an end and the U.S. Army refocused its attention on the threat of a Soviet ground offensive in Europe, Army leaders began to rethink some aspects of the air mobility concept. Before the war, the Army had only a limited aviation capability. But by the end of the war, the Army had a substantial Air Force of its own—centred on the helicopter—and could take on missions that were previously the domain of the U.S. Air Force, but which were often ignored by that service.

These changes in tactics proved themselves during the Persian Gulf War, when U.S. attack helicopters could freely range the battlefield during the night, easily destroying Iraqi tanks and other vehicles. Large numbers of U.S. troops were also ferried deep inside Iraqi territory, establishing facilities for supporting the attack helicopters as well as ground troops. Once again, other countries adopted the U.S. tactics and brought their helicopters.

While helicopters have revolutionized infantry warfare, they have had less of an impact on other areas of combat. This is primarily because they are still relatively slow, vulnerable, and cannot carry the large payloads that fixed-wing aircraft can carry.

Other than infantry and anti-tank operations, helicopters have most notably been used for Combat Search and Rescue (CSAR), where they retrieve downed pilots deep inside enemy lines. This technique was really perfected during Vietnam, but several well-publicized rescues took place during the Bosnia crisis and later during the 1999 bombing of Yugoslavia. These helicopters are often equipped with highly sophisticated navigation systems and are supported by other armed helicopters and fixed-wing aircraft during their rescue mission.

Helicopters have also been used in the maritime surveillance and anti-shipping role. During the Falklands War in 1981, a British Lynx helicopter fired a missile and sank an Argentine submarine moored at dock. U.S. helicopters have also been equipped with missiles for attacking small ships and boats.

Other than search and rescue of downed aviators, the primary purpose of naval helicopters has been submarine hunting and over-the-horizon targeting. Helicopters hunting submarines can hover and lower a large sonar into the water using a winch and cable. They are far more mobile than a ship and are invulnerable to the submarine they are hunting. Helicopters equipped with radar are also used to detect targets that a ship's sensors cannot see because they are over the horizon. They relay this data to the ship and can also guide ship-launched missiles to their targets. This has helped change the role of surface warships from defensive platforms used to protect aircraft carriers, to offensive platforms capable of attacking other ships at long range. In addition, helicopters have proven their utility at clearing mines. By towing large sleds along the water, the helicopter can stay away from any potentially harmful mines.