As the United States Air Force entered the Viet Nam War in full mode in 1965, it was faced with multiple challenges. The missions varied from air superiority to ground support to counterinsurgency. The air force was able to meet these challenges through an evolution of both doctrine and equipment. When the air war began over North Viet Nam in 1965, the F-4 Phantom, the newest fighter-bomber in the USAF inventory, had no guns but utilized long range air to air missiles for defense. After a series of dogfights with the slower but more nimble Soviet built Mig-17s, the F-4s were modified to carry the M-61 gattling gun. The M-61 was developed in the late 1950s and fired 20mm projectiles. It was developed from the earlier M-39 gattling gun, which fired the standard .50 cal. rounds. The M-61 was a marked improvement over the M-39 in firepower, with the M-61 having three times the rate of fire of a long-barreled .50 cal. machinegun. Boeing B-52 Stratofortress bombers, designed for the strategic nuclear role, were modified to carry conventional bombs for carpet bombing missions against Viet Cong troop and supply concentrations. C-130 transports were also converted to gunships, firing both gattling guns and artillery at night on suspected Viet Cong positions. These planes were refined throughout the war in terms of both electronics and firepower. Transport aircraft also defoliated thick jungle underbrush and dropped flares in support of ground operations.
In both Gulf Wars, USAF doctrine was to destroy the entire spectrum of Iraqi targets within a week, unlike the gradual approach taken over North Viet Nam in the 1960s. These attacks were designed to destroy the Iraqi leadership, degrading their military capabilities and will to fight. Unlike both Korea and Viet Nam, these missions were coordinated with the air forces of several nations. As many as 700 sorties were flown on a daily basis with the A-10 Thunderbolt proving an effective tank killer. An important aspect of air operations in both Gulf Wars was the large number of tactical aircraft deployed. With few forward bases and a three-fold increase in aircraft over the Viet Nam War, an effective tanker fleet was imperative. While many KC-135 and C-130 tanker planes were beginning to show age, they remained effective in refueling the tactical air forces of the United States and other allied nations, whenever and wherever needed. Laser-guided weapons also came into use, providing precision strike capability for both isolated ground targets and strategic urban targets, as well as the global positioning system or GPS, from which to acquire targets from satellite plotting data. Once an area was secured, C-17 cargo planes, able to operate from short, unimproved runways, supplied the local population with needed food and building materials from which to renew their communities. Such aircraft have also provided relief on a global scale to areas suffering from the effects of earthquakes, tsunamis, diseases and other natural disasters, proving the USAF a true force for peace.