not directed by the north. Back in 1959 a Laotian Lieutenant Colonel of the minority Hmong tribe had been taken under the wing of the CIA effort in Laos. The highland Hmong were more aggressive than the lowland Lao and Vang Pao was quickly elevated to their leadership in hopes of creating a paramilitary force that would counter the Pathet Lao in the northeast. Historian John Prados believed that the need to keep the Vientiane government weak, and to give free rein to the Hmong army, flew in the face of fostering the type of national government that could defeat the Pathet Lao. During 1961, the first weapons were delivered to the Hmong and their training was begun. Nine CIA specialists, nine U.S. Army Special Forces personnel, and 99 Thai members of the Police Aerial Reconnaissance Unit (PARU) participated in the training and equipping of what became known as the Armée Clandestine or the secret army. The neutralization agreement forced the abandonment of the Hmong program, but that was not going to last long. Due to North Vietnamese violations of the agreement, President John F. Kennedy authorized a return to covert activities in 1963. The previous year the CIA and the Thai military had established "Headquarters 333" at Udon Thani, which acted as a joint U.S./Thai command center for covert military and intelligence collection activities in Laos. By the end of 1963, the numbers of the Hmong army had grown to 10,000. To supply the Hmong and Royal Lao armies with more firepower, the Thai government covertly dispatched artillery units to northeastern Laos. Logistical airlift for the covert effort was provided by Air America, Bird and Son, and Continental Air Services, all of which were CIA proprietary airlines. The next stage of the military evolution took place during mid-March 1964, when the USAF began Project Waterpump, a program to train Laotian, Thai, Hmong, and Air America aircrews in flight and maintenance of U.S.-supplied AT-28 Trojan ground-attack aircraft. This training was conducted by Detachment 6, 1st Air Commando Wing personnel at Udon Royal Thai Air Force Base, Thailand. The first mission in support of Vang Pao's forces took place on 25 May. Eventually, the Royal Laotian Air Force would consist of five wings of ten aircraft each. Water Pump could never produce enough pilots, however, since graduation rates barely exceeded the death rate of graduates, who simply flew until they died.