The "Contemporary Historical Evaluation of Combat Operations" (CHECO) report detailing air operations during the siege of Khe Sanh. Operation NIAGARA was a significant air effort in 1968 to disrupt a major offensive in northwestern I Corps near Khe Sanh. An extensive enemy build-up in the area foreshadowed a major offensive, with the objective of overrunning Khe Sanh and other friendly positions located along Route 9, the most readily accessible infiltration route for North Vietnamese forces into South Vietnam.