sorties only occurred when aircraft were returning to Thailand from Rolling Thunder missions carrying unexpended ordnance loads. They would then be directed to targets in northeastern Laos. Electronic tactical air navigation (TACAN) became an absolute necessity in Laos, where mountain peaks and unexpected inclement weather made flying extremely hazardous, especially for older aircraft. This problem was solved by establishing unmanned Air Force stations that broadcast continuous radio transmissions, allowing aerial navigation from fixed geographic reference points. The Air Force also emplaced TSQ-81 radar sites in the north and northeast to direct Rolling Thunder missions over North Vietnam. Rules of engagement During the entire covert war in Laos there was little love lost between the Air Force commanders at Udon Thani and Saigon and the embassy in Vientiane. Richard Secord, then an Air Force captain serving as liaison between the CIA and the Seventh Air Force, complained that: We were always trying to pry assets out of the Air Force at times and places they didn't want to go. You had to push'em, cajole'em, at times threaten them... My people were always trying to corrupt the process because the process itself simply was not structured for our kind of war... It was a continual frustration. Secord's criticism may have been a little extreme. The Department of Defense had created the 7th/13 Air Force at Udon in November 1965 for the express purpose of conducting the air war in Laos. According to historian Timothy Castle, Sullivan relegated the USAF commander and his staff "to the status of clerks hired to carry out his airpower decisions." The unconventional arrangement bred frustration and the 7th/13th constantly harped about the use of its air assets in northern Laos. There was constant criticism over the use of air power "serving targets" or utilizing modern fighter-bombers as "long-range artillery." It was very difficult for the USAF to grasp that a guerrilla force did not fight like a conventional army. The aerial rules of engagement applied in Laos (which prescribed the offensive action of pilots and the locations and circumstances under which offensive actions could be taken) were created to protect the civilian population of the country. To the American pilots that conducted the missions, however, they became complex to the point of incomprehensibility. The rules were constantly altered and elaborated upon by the political decision makers in Washington and Vientiane and bore little relation to the reality