Dangerously Close! USAF Close Air Support in the Southeast Asia War Close air support (CAS) -- sometimes called tactical air support -- gave American and South Vietnamese ground forces a tremendous military advantage. However, the U.S. Air Force had to relearn CAS tactics used during World War II and the Korean War. Because the USAF's high-speed combat jets flew too fast to provide effective support, aircrews initially made due with outdated aircraft. Lastly, the USAF had to create an effective system for controlling the large number of airstrikes over a small area. After all, the "close" in close air support really meant striking the enemy dangerously close to our own troops! Click on the following links to learn more about close air support during the Southeast Asia War. Early Years, 1961-1964 On the Offensive, 1964-1969 Vietnamization, 1969-1973 OPERATION NIAGARA: A Waterfall of Bombs at Khe Sanh Click here to return to the South Vietnam: Build-Up and Engagement Overview.