Vinh Thanh Valley, 10 miles northwest of the 1st Cavalry Division's base at An Khe, was 12 miles long and less than 3 miles wide, heavily populated and firmly under Viet Cong control. Ten miles to the east lay the Suoi Ca Valley — which American soldiers, with the grim humor of men far from home, nicknamed "Happy Valley." Between them rose a chain of heavily forested mountains, climbing as much as 2,600 feet above the valley floors. A trail crossing those mountains earned another American name: the Oregon Trail. This was the terrain into which the 1st Cavalry's airmobile helicopters would attempt to insert troops and, in theory, destroy the VC 2nd Regiment — approximately 2,000 men — believed to be operating in the area. The immediate trigger was intelligence suggesting the regiment might attack the Vinh Thanh Civilian Irregular Defense Group camp. The longer-standing objective was securing Highway 19, the crucial road connecting the coast to Pleiku and the Central Highlands.

The operation opened with artillery fire intended to disrupt any planned VC attack and prepare the landing zones. The first helicopter insertion went into Landing Zone Hereford on a ridge overlooking the Vinh Thanh valley and the Special Forces camp three miles distant. Shortly after landing on May 16, Company B, 2nd Battalion, 8th Cavalry Regiment made contact with a Viet Cong battalion on a ridge near the landing zone. Bad weather grounded much of the available air support, leaving the Americans surrounded and fighting in the rain. During a break in the weather, Company C, 1st Battalion, 12th Cavalry Regiment landed and moved up to support them. The fight lasted through the night, at close quarters. When daylight came and the Viet Cong withdrew, they had left 38 of their dead on the ridge. Twenty-eight Americans had been killed — soldiers from Company B who had made it to Vietnam and then to that particular ridge on that particular night.

General Norton, commanding the operation, reassessed after Landing Zone Hereford. He had watched his soldiers take casualties in exactly the kind of direct engagement the Viet Cong were prepared for, and he changed course. Search-and-destroy was suspended temporarily. The new strategy was encirclement: try to ring the area where the VC were believed to be, cut off escape routes, and use artillery and airstrikes to pressure them while allied units — eventually four American battalions, one South Vietnamese, one South Korean, and one Civilian Irregular Defense Group battalion of Montagnard fighters with Special Forces advisors — waited to ambush units attempting to flee. On May 26, a clash at Landing Zone Monkey put an American company briefly under siege and cost another helicopter. By late May, it was clear that most of the Viet Cong regiment had slipped away. The operation was officially terminated on June 5.

The U.S. declared Operation Crazy Horse a success. American commanders reported an estimated 507 Viet Cong killed. The cost was 83 Americans dead, 14 South Koreans, 8 South Vietnamese, and an unrecorded number of Montagnard fighters whose lives, apparently, did not require a final count. Those figures carried their own weight, apart from the question of whether the operation achieved its aims. The VC 2nd Regiment had not been destroyed; it had avoided destruction. Three months later, the 1st Cavalry was back in Bình Định Province with Operation Thayer, trying again to eliminate North Vietnamese and Viet Cong influence in the same region. The cycle of operations and withdrawals continued.

Operation Crazy Horse left behind something more durable than its body counts: a tactical lesson that would be debated for years. In heavily forested mountains, the number of places where helicopters could actually land was sharply limited. The enemy knew this. Communist forces could study the terrain, identify the viable landing zones, and be waiting — either to contest the landing directly or to ambush soldiers as they fanned out into the trees. Airmobility, the 1st Cavalry's great innovation, was not equally effective everywhere. The valleys and mountains of Bình Định Province were not the open terrain where air assault showed to best advantage. The lesson was real, and the Army acknowledged it. Whether it was fully absorbed before the next operation — and the one after that — is a different question.