noticeable of which was more realistic, and thus more dangerous, combat training. In combat simulations Air Force pilots flew as aggressors employing enemy tactics. By 1975 their training had evolved into Red Flag at the U.S. Air Force Weapons and Tactics Center at Nellis Air Force Base in Nevada, in which crews flew both individual sorties and formations in realistic situations, gaining experience before they entered actual combat.
The vulnerability of air bases to enemy attack and sabotage had long been the Achilles heel of land-based air power. In western Europe, living under the threat of a massive Warsaw Pact air offensive and land invasion, the U.S. Air Force spearheaded an active program to improve the survivability and readiness of air bases. The effort was marked by the construction of thousands of reinforced concrete aircraft shelters and other hardened facilities, alternate runways, rapid repair elements, chemical weapons protection, and a host of other defensive measures.
The Air Force's post-Vietnam rebuilding also involved applying improved technology. The battle for control of the skies over North Vietnam underscored the need for a dogfighting aircraft that featured maneuverability before speed―one armed with missiles and cannon. Begun in the late 1960s and operational in the mid-1970s, the F-15 Eagle and the F-16 Fighting Falcon filled this need. The struggle against radar-guided antiaircraft artillery and surface-to-air missiles in Vietnam encouraged the Air Force to pursue stealth technology utilizing special paints, materials, and designs that reduced or eliminated an aircraft's radar, thermal, and electronic signatures. Operational by October 1980, both the B-2 stealth bomber and the F-117 Nighthawk stealth fighter featured detection avoidance.
Other Vietnam War technologies included precision guided missiles and bombs. From April 1972 to January 1973 the United States used over 4,000 of these early "smart weapons" in Vietnam to knock down bridges and destroy enemy tanks. Continued development of laser-guided bombs and electro-optically-guided missiles offered the prospects of pinpoint, precision bombing on which traditional Air Force doctrine rested―the destruction of chokepoints in an enemy nation's industrial web with economy of force and without collateral damage. These technologies, which afforded a strike precision far beyond that available to earlier air power thinkers, sparked a revision of the traditional doctrine of strategic bombing. This revision took two forms. First, the Air Force, to overcome numerically superior Warsaw Pact forces, cooperated with the Army in updating the tactical doctrine of AirLand Battle promulgated in Field Manual 100-5 in 1982. The Air Force would make deep air attacks
