Operation Delaware was a joint military operation launched during the Vietnam War. It began on Friday, April 19, 1968, with troops from the United States and the Army of the Republic of Vietnam (ARVN) moving into the A Shau Valley. The A Shau Valley was a vital corridor for moving vast amounts of supplies coming from the Ho Chi Minh Trail and was used by the People's Army of Vietnam (PAVN) as a staging area for numerous attacks in northern I Corps. Other than small, special operations reconnaissance patrols, American and South Vietnamese forces had not been present in the region since the Battle of A Shau in 1966, when a U.S. Special Forces camp located there was overrun.
In January 1968, General Creighton W. Abrams, deputy commander of Military Assistance Command, Vietnam, ordered the 1st Cavalry Division (Airmobile) to move north from the Central Highlands to support the Marines. The 1st Cavalry Division, an airmobile division with 20,000 men and nearly 450 helicopters, had the most firepower and mobility of any division-size unit in Vietnam.:42&209 When it arrived in I Corps, the 1st Cavalry Division fought toe-to-toe with the enemy during the Tet Offensive. It was fully engaged with the PAVN at Khe Sanh when its commander, Maj. Gen. John J. Tolson, was ordered to prepare plans for the massive air assault into the A Shau Valley: Operation Delaware.
After gaining control of the A Shau Valley in March 1966 the PAVN fortified it with powerful crew-served 37mm antiaircraft cannons, some of them radar controlled. They also had rapid firing twin-barreled 23mm cannons and many 12.7mm heavy machine guns to contribute to their air defenses. The A Shau Valley soon evolved into a major logistics depot for the PAVN, with storage locations often located in underground bunkers and tunnels. Because of this strength on the ground, and the relative geographic isolation of the valley, the U.S. and its allies conducted little offensive activity in the area except for air attacks, and those were limited by steep, mountainous terrain often cloaked under clouds and prone to sudden, violent changes in weather. Because of the very limited air mobility of the Marines in I Corps, no ground operations of any significance had been launched in the A Shau.:143–9
By early April 1968, the PAVN had just suffered two of their most significant defeats of the war: the Tet Offensive and at Khe Sanh, which cost them more than 40,000 men. But the PAVN still had the ability to regain the initiative in the northernmost part of I Corps. That ability came in part from isolated base areas like the sparsely populated A Shau Valley, running north-south along the Laotian border 30 miles south of Khe Sanh, where troops and supplies were moved into South Vietnam as the PAVN prepared for another battle — at a time and place of its choosing. The A Shau, a mile-wide bottomland flanked by densely forested 5,000-foot mountains, was bisected lengthwise by Route 548, a hard-crusted dirt road.:182–192 :347–9 
The battle began on April 19, 1968, after preparatory B-52 and tactical bombings of PAVN antiaircraft and troop positions. Troops of the 1st Cavalry Division were inserted into the north of A Shau Valley by helicopter, as the 1st Brigade, 101st Airborne Division; the 3rd Regiment, 1st ARVN Division; and the 3rd ARVN Airborne Task Force provided the blocking force on the southeast fringe of the valley on both sides of Route 547 that lead to Hue. Poor weather and anti-aircraft fire made flying very dangerous.:184–5
The 1st Cavalry Division's 1st and 2nd brigades numbering about 11,000 men and 300 helicopters attacked the north end of the valley and leapfrogged south, while its 2nd brigade remained at Khe Sanh, continuing offensive operations to the Laotian border.:185 The operation required a radio relay site so the engaged brigades could communicate with Camp Evans near the coast or with approaching aircraft. On the eastern side, midway up the valley, was a perfect spot: the 4,878-foot Dong Re Lao Mountain. The 1st Cavalry Division's headquarters dubbed it “Signal Hill.”:144–6 A 30-man long-range reconnaissance patrol (LRRP, or “Lurp”) from Company E, 52nd Infantry (LRP), commanded by Captain Michael Gooding, would be dropped by helicopter onto Signal hill where it would fight a two day battle with PAVN forces.
The 1st Cavalry Division established fire support bases in the north and then rapidly continued air assaults south through the valley. The abandoned A Lưới airstrip, midway in the valley, was captured. The first cargo aircraft, a C-7 Caribou, landed on 2 May. After further improvements to the airstrip, the first C-130 Hercules landed on 4 May. As the 1st Cavalry Division kept sweeping south through the valley it linked with the other allied units that served as blocking forces and uncovered large caches of weapons, vehicles, ammunition, and rice. US and ARVN troop extraction started on 10 May, with the operation terminating on 17 May.:147–9
Despite hundreds of B-52 and jet air strikes, the enemy shot down a C-130, a CH-54 Skycrane, two CH-47 Chinooks, and nearly two dozen UH-1 Hueys. Many more, though not shot out of the sky, were lost in accidents or damaged by ground fire. The 1st Cavalry Division suffered more than 130 dead and 530 wounded. Bad weather aggravated the loss by causing delays in troop movements, allowing a substantial number of PAVN to escape to safety in Laos. Nevertheless, Operation Delaware was hailed as a success and the withdrawal of US and ARVN troops made it possible for PAVN forces to quickly regain control of the valley.:148–9
Maj. Gen. Tolson, in summing up the weather's impact on his division’s airmobile operations, said, “According to the long range forecast based on old French records, April was supposed to have been the best month for weather in the A Shau Valley. As it turned out, May would have been a far better month––but you don’t win them all.”:192 That lesson, however, would not be lost on U.S forces, specifically, the U.S. Marines who assaulted A Shau Valley in January 1969 in Operation Dewey Canyon, and the 101st Airborne Division, who returned in May 1969 during Operation Dewey Canyon II and stormed Dong Ap Bia Mountain, commonly known as the Hamburger Hill, just southwest of Signal Hill, on the opposite side of the valley. The NVA lost those battles, too, yet they returned to A Shau, prompting criticism of American tactics.:148–9 But with South Vietnam’s wild and remote borders over twice as long as the trenches in France during World War I—which were manned by millions of troops—there simply were not enough allied soldiers to secure them. With that limitation in mind, airmobile divisions such as the 1st Cavalry and 101st Airborne demonstrated that a unit need not be based in the hinterlands to operate and destroy the enemy there.:192
- Robert C. Ankony, Lurps: A Ranger's Diary of Tet, Khe Sanh, A Shau, and Quang Tri, revised ed., Rowman & Littlefield Publishing Group, Lanham, MD (2009), pp.157–72. 
- Stanton, Shelby (1987). Anatomy of a Division: The 1st Cav in Vietnam. Presidio Press. p. 111.
- Tolson, John (1973). Vietnam Studies: Airmobilty 1961–1971. Department of the Army. p. 178.
- Westmoreland, William (1976). A Soldier Reports. Doubleday. p. 347. ISBN 9780385004343.
- Robert C. Ankony, "No Peace in the Valley," Vietnam magazine, Oct. 2008, pp. 26–31.
- Robert Pisor, The End of the Line: The Siege of Khe Sanh. New York: W. W. Norton (1982), p. 181.
- Rangers at War, Shelby L. Stanton, Ivy Books: New York (1992)