Because of the U.S. air campaign, American bases came under greater threat of Viet Cong retaliatory attacks. Thus, in March 1965, on President Johnson’s orders, 3,500 U.S. Marines arrived to protect Da Nang air base. These Marines were the first U.S. combat troops to be deployed in Vietnam. Then in April 1965, when the U.S. government’s offer of economic aid to North Vietnam in exchange for a peace agreement was rejected by the Hanoi government, President Johnson soon sent more U.S. ground forces, raising the total U.S. personnel strength in Vietnam to 60,000 troops. At this point, U.S. forces were authorized only to defend American military installations.
(Taken from Vietnam War – Wars of the 20th Century – Twenty Wars in Asia – Vol. 5)
Throughout the Vietnam War, the United States launched other aerial operations (Steel Tiger, Tiger Hound, and Commando Hunt) on the Ho Chi Minh Trail to try and stop the flow of men and materiel from North Vietnam to South Vietnam, but all of these ultimately proved unsuccessful.
Over the course of the war, the Ho Chi Minh Trail system expanded considerably into an elaborate network of small and wide roads, foot and bike paths, and concealed river crossings across a vast and ever-increasing area in the eastern regions of Laos and Cambodia. With 43,000 North Vietnamese and Laotian laborers, dozens of bulldozers, road graders, and other road-building equipment working day and night, by December 1961, the Trail system allowed for truck traffic, which became the main source of transporting men and supplies for the rest of the war. Apart from construction crews, other units in the Ho Chi Minh Trail were tasked with providing food, housing, and medical care, and other services to soldiers and transport crews moving along the system. To counter U.S. air attacks, which intensified as the war progressed, the Trail system was massively fortified with air defenses, eventually bristling with 1,500 anti-aircraft guns. Supply convoys also traveled only at night to lessen the risk of U.S. air attacks.
But because of the U.S. air campaign, American bases came under greater threat of Viet Cong retaliatory attacks. Thus, in March 1965, on President Johnson’s orders, 3,500 U.S. Marines arrived to protect Da Nang air base. These Marines were the first U.S. combat troops to be deployed in Vietnam. Then in April 1965, when the U.S. government’s offer of economic aid to North Vietnam in exchange for a peace agreement was rejected by the Hanoi government, President Johnson soon sent more U.S. ground forces, raising the total U.S. personnel strength in Vietnam to 60,000 troops. At this point, U.S. forces were authorized only to defend American military installations.
Then in May 1965, in a major effort to overthrow South Vietnam, Viet Cong and North Vietnamese forces launched attacks in three major areas: just south of the DMZ, in the Central Highlands, and in areas around Saigon. U.S. and South Vietnamese forces repulsed these attacks, with massive U.S. air firepower being particularly effective, and in mid-1965, Viet Cong and North Vietnamese forces retreated, and the danger to the Saigon government passed. By that time also, President Johnson agreed to the U.S. military’s request and sent more troops to Vietnam, raising the total to 184,000 by the end of 1965. More crucially, he now authorized U.S. forces to not merely defend U.S. facilities, but to undertake offensive combat missions, in line with American military doctrine to take the war to the enemy.
Meanwhile in June 1965, South Vietnam’s political climate eased considerably with the appointment of Nguyen Cao Ky as Prime Minister and Nguyen Van Thieu as (figurehead) Chief of State. The new South Vietnamese regime imposed censorship and restrictions on civil liberties because of the unstable security situation, as well as to curb widespread local civilian unrest. In 1966, Prime Minister Ky quelled a Buddhist uprising and brought some stability to the South Vietnamese military. Ky and Thieu were political rivals, and after Thieu was elected president in the 1967 presidential election, a power struggle developed between the two leaders, with President Thieu ultimately emerging victorious. By the late 1960s, Thieu had consolidated power and thereafter ruled with near autocratic powers.
During the Vietnam War, the United States, which soon was joined with combat forces from its anti-communist allies Australia, New Zealand, South Korea, Thailand, and the Philippines, began to take direct command of the war in what was called the period of the “Americanization” of the war, relegating the South Vietnamese military to a supporting role. Nevertheless, President Johnson imposed restrictions on the U.S. military – that it was to engage only in a limited war (as opposed to a total war) that was sufficiently aggressive enough to deter North Vietnam from attacking South Vietnam, but should not be too overpowering to incite a drastic response from the major communist powers, China and the Soviet Union.
The United States was concerned that China might intervene directly for North Vietnam (as it had done for North Korea in the Korean War), or worse, that the Soviet Union might invade Western Europe. A consequence of U.S. policy in Vietnam to not incite a wider war with China and the Soviet Union meant that U.S. forces could not invade North Vietnam, and that U.S. bombing missions in North Vietnam were to be screened so as not to kill or harm Chinese or Soviet military personnel there or destroy Chinese and Soviet assets (e.g. ships docked at North Vietnamese ports). Thus, U.S. ground forces were limited to operating in South Vietnam, where subsequently nearly all of the land fighting took place. Even then, the U.S. high command was confident of success, and General William Westmoreland, commander of U.S. forces in Vietnam, predicted American victory over the Viet Cong/NLF by the end of 1967.
To achieve this goal, the U.S. military employed the “search and destroy” strategy (which was developed by the British in the 1950s), where U.S. intelligence would locate large Viet Cong/NLF concentrations, which would be destroyed using massive American firepower involving air, artillery, infantry, and in some cases armored, units. U.S. military planners believed that the use of overwhelming force would inflict such heavy losses that the Viet Cong would be unable to replace its manpower and material losses, ultimately leading to the defeat of the southern insurgency.
During the Vietnam War, the number of American troops over the Viet Cong/NLF did not reach the 10:1 ratio that is conventionally taken as required to quell an insurgency. As a result, the U.S. military measured the success of search and destroy missions not by seizing and holding territory, but by quantifying enemy losses, namely, the amount of Viet Cong/NLF stockpiles and armed caches captured or destroyed, the number of enemy strongholds overran, and most important, the number of insurgents killed (“body count”). The U.S military focused its search and destroy missions around the major Viet Cong areas in the central region near Da Nang and Qui Nhon, the central Mekong Delta, and in the west and north of Saigon.
General Westmoreland believed that the Viet Cong’s greatest threat to South Vietnam was in the areas near Saigon, particularly in the western frontier regions adjacent to the Cambodian border, in locations called the Iron Triangle, and Battle Zones C and D (Figure 5). For most of the war, U.S. forces carried out successive search and destroy operations in these areas, which ultimately proved only partially successful. General Westmoreland’s other plan was to establish a network of American strategic strong points in South Vietnam from where U.S. forces would launch search and destroy operations. He envisioned that search and destroy operations would be followed by clear and hold missions, where South Vietnamese forces would re-establish control over former Viet Cong/NLF areas. In December 1965, because of aggressive U.S. combat tactics, the Viet Cong was forced to return to guerilla warfare, and only fought in the open when the odds were clearly in its favor.
In June 1965, U.S. forces launched their first major offensive of the war, targeting a Viet Cong hideout northwest of Saigon, which was followed in 1966 with several major operations in other Viet Cong/NLF strongholds: Operation Crimp (January 1966) in the Cu Chi District, 40 kilometers northwest of Saigon where a yet undiscovered massive Viet Cong underground tunnel complex was located; Operation Birmingham (April-May 1966) in War Zone C, a Viet Cong/NLF stronghold located 80 kilometers northwest of Saigon, which involved U.S. and South Vietnamese troops, supported by air and armored units; Operation Attleboro (September 1966) in Tay Nihn Province, where U.S. and South Vietnamese forces preempted a planned Viet Cong attack on the Suoi Da U.S. Special Forces base and after six weeks of several small engagements, inflicted heavy Viet Cong casualties and seized large quantities of enemy supplies.
In early 1967, further sweeps were made on Viet Cong/NLF strongholds northwest of Saigon. In Operation Cedar Falls (January 1967), 30,000 American and South Vietnamese troops attacked the Iron Triangle, a 60-square mile Viet Cong/NLF stronghold, and seized control of the area (including capturing a stockpile of weapons, food, supplies, and documents). U.S. forces encountered no major resistance as the bulk of Viet Cong forces had withdrawn earlier from the area. Then in Operation Junction City (February 1967), 30,000 U.S. and 5,000 South Vietnamese troops, supported by air, artillery, and armored units, swept down on War Zone C, which was believed to be the insurgent command headquarters called COSVN (Central Office for South Vietnam), and seized large quantities of Viet Cong/NLF stockpiles, but failed to locate major enemy units.