History of Vietnam since 1945 unstable as no government could keep power for long. There were more coups, often more than one every year. The Communist-run Viet Cong expanded their operation and scored some significant military victories during this period. In 1965, US President Lyndon Johnson sent troops to South Vietnam to secure the country and started to bomb North Vietnam, assuming that if South Vietnam fell to the Communists, other countries in the Southeast Asia would follow, in accordance with the domino theory. Other US allies, such as Australia, New Zealand, South Korea, Thailand, the Philippines, and Taiwan also sent troops to South Vietnam.
Vietnam War gun of the US army at the time and many of them were put on helicopters, to provide suppressive fire. The MAC-10 machine pistol was supplied to many special forces troops in the midpoint of the war. Two aircraft that were prominent in the war were the AC-130 "Spectre" Gunship and the UH-1 "Huey" gunship. The AC-130 was a heavily armed ground-attack aircraft variant of the C-130 Hercules transport plane. The Huey is a military helicopter powered by a single, turboshaft engine, and approximately 7,000 UH-1 aircraft saw service in Vietnam. The U.S. heavily armored, 90 mm M48A3 Patton tank