The Central Highlands of II Corps were not just terrain — they were a strategic problem. The mountains and dense forests that spread across Kon Tum Province masked a network of supply routes carrying ammunition and troops southward. General William Westmoreland's command had committed to contesting these routes, but the environment consistently favored defenders who knew the ground. In June 1966, North Vietnamese and Viet Cong forces exploited the monsoon season to mount a major offensive, banking on the rain and low cloud that reduced American air superiority. The ARVN 42nd Regiment, 22nd Division, bore the initial weight of that offensive at Toumorong, and its garrison needed help. Brigadier General Willard Pearson assembled a substantial rescue force: three battalions of the 101st Airborne, a battalion of the 1st Cavalry Division (Airmobile), and two Civilian Irregular Defense Group companies.

On June 3rd, ARVN elements moved north from Đắk Tô by road while the 1st Battalion, 327th Infantry was helicoptered into blocking positions. Three days later the Toumorong garrison was relieved — the operation's nominal objective met in under a week. But the North Vietnamese were not withdrawing. They were consolidating. In the early hours of June 7th, at 02:15, an estimated PAVN battalion struck the American positions. The first assault was beaten back; two more followed through the night. It was not until nine in the morning, when air support and artillery finally broke the pressure, that the fighting subsided. By that afternoon the 2nd Battalion, 502nd Infantry had dropped into a landing zone northwest of the battle, and another pitched engagement had begun before the sun set — with 77 North Vietnamese soldiers killed in that single day's fighting alone.

The most harrowing day came on June 9th. Company C of the 2nd Battalion, 502nd Infantry was fighting northwest of Toumorong when the situation collapsed around them. They found themselves trapped in a bowl, North Vietnamese forces pressing on three sides, their perimeter in danger of being overrun. When air support arrived overhead, the Company C commander, Captain Bill Carpenter, made a decision that has echoed through accounts of the war ever since. He radioed the forward air controller: 'Lay it right on top of us... they are overrunning us, we might as well take some of them too.' Two F-4C Phantom jets dropped napalm on his position — inside and outside the perimeter — and broke the attack. The soldiers who survived that afternoon were extracted only after Company A of the 2nd Battalion, 502nd linked up with them after midnight, twenty-three hours after the battle had started.

The final phase of Operation Hawthorne was decided not by infantry but by firepower on a scale that Vietnam would become associated with. On June 10th, fifteen B-52 Stratofortresses dropped 270 tons of bombs on suspected North Vietnamese positions. Three days later, twenty-four B-52s dropped 432 tons on the same area. American troops helicoptered into the bombed zone reported the strikes had been devastatingly effective, capturing several stunned survivors. After that, contact with North Vietnamese forces was minimal. The operation formally concluded on June 21st. The toll reflected the intensity of what had occurred: 48 Americans and 10 South Vietnamese soldiers killed, 239 Americans and 29 South Vietnamese wounded. The U.S. and ARVN claimed 479 North Vietnamese killed in direct combat, with estimates of hundreds more. Every number represents people — soldiers on all sides who had come a long way to fight over jungle ridgelines in a monsoon.