During the Korean War, helicopters were used to insert troops into combat zones, to deliver arms, and to evacuate the wounded. During the Vietnam War this form of aerial transport evolved to become an "air cavalry" platform, rapidly ferrying infantry to where they were most needed, when they were needed. As U.S. military involvement in the Vietnamese conflict deepened, helicopters began to operate near enemy positions, and a need was seen to arm them with appropriate weaponry — thus was born the concept of the helicopter gunship.
As the Vietnam War escalated, the Bell UH-1 Iroquois, better known as the "Huey", was deployed in increasing numbers, primarily for the transportation of troops and for medical evacuation. While gunship variants of the Huey were armed with side-door machine guns and rocket pods, they only served as an interim solution, lacking armament required to protect the crew and to survive in high-intensity combat.
Back in 1962, a confidential Bell Helicopter project had created a conceptual design for what would come to be called an attack helicopter. The design incorporated a chin-mounted automatic grenade launcher, a ventral cannon and wing-mounted missile launchers. Its crew of two were arranged in tandem, giving the rotorcraft a slim frontal profile, making it a harder target to hit from the ground. The weapons operator sat lower than and in front of the pilot, providing the best possible fields of vision.
Bell began to shop around a mockup and in August 1964, the U.S. Army's Advanced Aerial Fire Support System program issued a formal request for proposals. The AAFSS called for an attack helicopter with a speed of over 200 knots (230 mph), equipped with overwhelming firepower capacity. In March 1966 the Army contract was awarded to a competing design from Lockheed. Over at Bell Helicopter it was estimated that Lockheed, with no background in rotary-wing aircraft development, would need at least three to four years to turn their complex design for a heavy, high speed attack helicopter into a production model. The engineers at Bell focused their efforts on a smaller, lighter gunship design, which was given the in-house designation Model 209.
Government regulations prevented the Army from buying a new type of helicopter without holding a formal design competition, and Bell had just lost out on such a bidding competition to Lockheed. That restriction did not apply to a modification of an existing model. The Army had already bought Huey models UH-1A through UH-1F, so the bright staff at Bell Helicopter decided to position the Model 209 as a modified UH-1, designated "UH-1G", and to offer their design as an interim platform to be used in the field while the Army waited for Lockheed to deliver production models.
In April 1966, the Army signed a production contract for 110 aircraft. "Cobra" was added to the UH-1 Huey's nickname to produce the name HueyCobra. Since "UH" stands for "utility helicopter", the Army gave the new model the formal designation AH-1G HueyCobra, where the "A" stands for "Attack". The first HueyCobras arrived in Vietnam on August 29, 1967. Meanwhile, Lockheed’s projected ready-date steadily slipped forward — their project would finally be canceled in 1972.
Between 1967 and 1973, Bell Helicopter would build 1,116 AH-1s for the U.S. Army, and it served as the backbone of the Army's attack helicopter fleet during that epoch. About 300 Cobras were lost in Vietnam, with about a third of those lost in non-combat related accidents.
The Cobra pioneered a new concept in helicopter armament, with a turret beneath the chin that was controlled by the weapons operator, and four hard-points beneath two "stub wings" placed at the sides of the fuselage, for gun pods and rocket launchers that were controlled by either crew member. The stub wings did not serve to provide aerodynamic lift — their only purpose was enabling the AH-1 to carry more firepower.
The HueyCobra was designed to escort troop-carrying Bell UH-1 Iroquois utility helicopters to the battlefield, where its superior speed enabled a quick dash to the landing zone. There, its attack capabilities was used to soften up enemy units waiting in ambush. The AH-1 was also used in a close air support role. In an alternate role, they were dispatched to loiter over contested regions, attacking targets of opportunity like exposed enemy infantry. As the U.S. Army acquired experience in Vietnam, AH-1 Cobras began to be teamed with scout helicopters on hunter-killer missions to reveal and attack enemy positions. Such missions are described in 19 Minutes to Live - Helicopter Combat in Vietnam: A Memoir by Lew Jennings, among other unforgettable experiences.