When the Tet Offensive was launched in January 1968, the goal was to seize nearly every major South Vietnamese city, hoping to provoke a general uprising among the population. The People's Army of Vietnam (PAVN) and the Viet Cong (VC) suffered heavy casualties in that failed effort and the planned culminating phases of the campaign were limited in scope. The second phase of the Tet Offensive began on April 29 and was called "Little Tet"; its primary targets were Saigon, the South Vietnamese capital city, and Đông Hà, the northernmost town in South Vietnam and the location of the U.S. Marine Corps Dong Ha Combat Base. This strategically important base was used to support Marine positions along the Demilitarized Zone separating the two Vietnamese nations.
A buildup of PAVN and Viet Cong forces in regions to the southwest of Da Nang had made it evident that the major port city was an intended target of the second phase of the Tet Offensive, as originally planned. Intelligence reports received during that time indicated that the North Vietnamese were planning a major attack on Da Nang during late July. The Da Nang Air Base would have been a prime objective. This was a major base where U.S. Army, Air Force, and Marine Corps units were stationed and during the Vietnam War it was considered to be one of the world's busiest airports.
To preempt and prevent an offensive on Da Nang from the southwest, two U.S. Marine Corps operations were undertaken, namely Operation Allen Brook and Operation Mameluke Thrust.
Operation Allen Brook
U.S. reconnaissance activities during April 1968 indicated that regular North Vietnamese units were deploying to positions in Quảng Nam Province in the South Central Coast region of Vietnam. Marine command concern focused on the Go Noi Island sector, about 25 kilometers south of Da Nang. Communist forces had controlled the area for years and had established long-standing political and military command infrastructures, creating a relative safe haven for North Vietnamese and Viet Cong military units. The area to the north of Go Noi was nicknamed "Dodge City" by the Marines, due to the frequent ambushes and firefights there. In combination the areas formed stronghold and base area for the North Vietnamese Army and the Viet Cong.
On the morning of May 4, two Marine companies supported by tanks crossed onto Goi Noi Island, opening what was to become Operation Allen Brook, which continued through August 24. During this operation the enemy was discovered to have been staging forces in the region, leading the Marines to believe that they had thwarted a planned assault on Da Nang. Casualties on both sides were heavy. Through the end of May, the Marines reported over 600 enemy killed, while sustaining 138 killed, 686 wounded and another 283 non-battle casualties. The number of heat-induced "non-battle casualties" had soared due to extreme high temperatures averaging almost 110 degrees. In many engagements, the number of heat casualties equaled or exceeded the number of killed and wounded.
Operation Mameluke Thrust
Concern over a buildup of enemy forces near the Thuong Duc Special Forces Camp led the III Marine Amphibious Force to direct the 1st Marine Division to conduct a spoiling attack in a region known to the Marines as "Happy Valley". Happy Valley was home to a major VC/PAVN base camp and was used by Communist forces for storage areas and as a supply infiltration route. Soldiers and materials moved from the Laotian border region to positions near the Da Nang vital area had created a threat to the Da Nang Air Base, the Red Beach Base Area, which was a logistics and support base complex, Da Nang port facilities, and Marble Mountain Air Facility, which was used by USMC helicopters. The very purpose for which the Thuong Duc Camp had been established was to monitor Communist infiltration into the Da Nang vital area.
This spoiling attack was codenamed "Operation Mameluke Thrust" and continued from May 19 through October 23. By the operation's conclusion, the Marines had suffered 269 dead and 1,730 wounded, while PAVN had suffered 2,728 killed and 47 captured. The expected July ground assault on Da Nang did not materialize and the Marines attributed this fact to the successful execution of Operation Mameluke Thrust.
The author of Guns Up!: A Firsthand Account of the Vietnam War served as a machine gunner with the 5th Marine Regiment and was wounded three times, having arrived in Vietnam at the age of eighteen, at the height of the Tet Offensive. In his popular memoirs he recounts participating in combat operations in "Dodge City" and "Happy Valley".