Vietnamese infiltration routes then developing in the Laotian panhandle. On 19 May 1964 low-level photo reconnaissance flights (codenamed Yankee Team) over southern Laos were authorized and launched by RF-101 Voodoo aircraft. When they were fired upon during a mission, escort aircraft were provided. Two days later American aircraft began flying low-level photo recon missions over the northern part of the country, serving as the beginning of the American aerial commitment to the covert war. Covert war For the Americans, Laos became almost exclusively an air war, a reversal of the role air power played in the conflict in neighboring South Vietnam. In Laos, the USAF applied conventional air power in the support of an unconventional ground war. The mission of the USAF was to seal off the southern Mekong River Valley, thus providing a buffer for Thailand; insulating the Vientiane government from direct communist threat; draining PAVN manpower and resources; and interdiction of the approaches to the Ho Chi Minh trail. For U.S. interests, the aerial interdiction effort against the trail and the protection of Thailand were preeminent, and they became the raison d'être for the covert war in the northeast. According to U.S. Secretary of State Dean Rusk, after 1964 and the increasing U.S. commitment to South Vietnam, "Laos was only the wart on the hog." Originally, the American arrangement in Laos was based on the premise that the situation in South Vietnam would be controlled within a year or two. A holding action in Laos was all that was thought necessary. No one expected that the conflict would last ten years. Air Force historian Colonel Perry F. Lamy described Washington's view of the situation succinctly: Since the fate of Laos did not depend on a military solution in the air or on the ground in Laos and could only be decided by the outcome in Vietnam, winning the war against the DRV in northern Laos was not the objective. Instead, maintaining access to the country was paramount and keeping the Royal Lao government in power became the primary objective. For Hanoi, Laos was also a "limited war" with goals and objectives that were tied to its continued use of the Ho Chi Minh trail. The covert nature of the North Vietnamese logistical effort through Laos also had to be maintained in order to support the fiction that the conflict in South Vietnam was a popular uprising that was