Operation Delaware/Operation Lam Son 216 was a joint military operation launched during the Vietnam War. It began on 19 April 1968, with troops from the United States and the Army of the Republic of Vietnam (ARVN) moving into the A Sầu Valley. The A Sầu Valley was a vital corridor for moving military 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 March 1966, when a U.S. Special Forces camp located there was overrun.

The Battle of A Shau was waged in early 1966 during the Vietnam War between the People's Army of Vietnam (PAVN) and the forces of the United States and South Vietnam. The battle began on March 9 and lasted until March 10 with the fall of the U.S. Army's Special Forces camp of the same name. The battle was a strategic victory for the PAVN in that they were able to take control of the A Shau Valley and use it as a base area for the rest of the war.