the trail grew further during the 1960s. Detecting Viet Cong movements on the Ho Chi Minh trail was exceedingly difficult. The trail was a complex collection of interconnecting footpaths. The flexibility afforded by its complexity meant multiple routes could be traversed from north to south. As such, it was easy to shift to a different route if the security of one area was compromised. Furthermore, the length of the trail and the small number of persons using it on any given segment, coupled with its flexible nature made detection all but impossible. In attempts to combat troop and supply movement along the trail, the CIA and U.S. military set up heat and movement sensors along the trail to track enemy movement. U.S. forces also attempted to use air dropped listening devices to track enemy troops and pinpoint Viet Cong movements. 1959 also saw the arrival of William Colby in the region, and it became increasingly noticeable throughout 1959 that Diem was becoming paranoid regarding security issues and the military. This time saw a constant back and forth between Diem and Nhu over control of the military in the region. The year 1959 saw Diem's authority quickly being lessened, as Tran Quoc Bhu had insisted upon it. The CIA had very few contacts in the Viet Cong ranks or North Vietnam at the time. Many of the contacts that they had were double agents run by the Viet Cong. Much of the intelligence gathered regarding North Vietnam was unreliable. U.S. and South Vietnamese military personnel believed that the bulk of North Vietnamese supplies were being shipped over the Ho Chi Minh trail, however, more than 80 percent of Northern supplies were sent by sea. U.S. Special Forces also began to train some Laotian soldiers in unconventional warfare techniques as early as the fall of 1959 under the code name Erawan. This was because after President Kennedy took power who refused to send more American soldiers to battle in Southeast Asia. Instead, he called upon the CIA to use its "tribal forces" in Laos and to "make every possible effort to launch guerrilla operations in North Vietnam with its Asian recruits." Hence, under this code name, General Vang Pao, who served the royal Lao family was recruited. He then recruited and trained his Hmong soldiers to ally with the CIA and fight against the communist North. Vietnam 1961 In April 1961, Lansdale,