The ending of the Rolling Thunder campaign against North Vietnam released a large number of aircraft for use in the interdiction campaign over the Ho Chi Minh Trail. The first Commando Hunt interdiction campaign started on 15 November 1968 and eventually seven such campaigns were flown over southern Laos, corresponding to wet or dry seasons as dictated by the monsoon climate of Southeast Asia. The campaigns were intended to reduce the flow of arms and men from North Vietnam to the South and to destroy as much equipment and ordnance as possible. However, the problems of finding and destroying targets on the Trail remained as difficult as ever and the resourceful North Vietnamese always found ways to keep the troops in South Vietnam supplied with enough arms and reinforcements. The US employed its full range of available air power in the Commando Hunt operations and also introduced a number of new weapons and techniques. The B-52s, tactical fighters and the AC-119 and AC-130 gunships played a major part in the campaigns and the AC-130 Spectre was claimed to be the most effective aircraft in killing trucks. Unfortunately, most of the evidence since the war indicates that the number of trucks killed and the amount of supplies destroyed was greatly exaggerated. The series of campaigns came to an end on 10 April 1972 when Operation Linebacker started and just weeks after North Vietnam had proved its success in resupplying troops in the field by launching the Spring Invasion.