The U.S.A. forces lost some firefights with the communist Vietnamese, but it won nearly every battle, and virtually every campaign. So why wasn’t the war won before the USA withdrew the last of its forces in 1973? There are many contributing factors, but the most significant and compelling single factor is that the Allied anti-communist military effort (consisting primarily of South Vietnam, USA, South Korea, Australia, and New Zealand forces) in South Vietnam was doomed to fail from the start because of strategic restrictions placed upon it. The most militarily significant of these restrictions can be best summarized with one word: Sanctuaries. Blackhorse fought an enemy for six years in and around War Zone C that was fully resupplied and reinforced from these hidden safe havens on the other side of the Cambodian border.
The shortest distance from North Vietnam at the DMZ through South Vietnam to Saigon is about 400 miles. It was an impossible task for North Vietnam to supply its army that far through South Vietnam because the NVA would be attacked the entire way by RVN and its Allied forces once it crossed the narrow DMZ. Instead, the NVA communist forces established its logistical bases and roads a few miles inside “neutral” Cambodia and Laos.
North Vietnam threatened the governments of both Laos and Cambodia, and forced them to allow it to bring its military supplies and reinforcements through the western parts of those two “neutral” countries. In addition, the NVA built scores of giant supply bases in both “neutral” countries. North Vietnam knew that the U.S. Congress and the United Nations prohibited ground interdiction to close those illegal supply lines.
The existence and importance of the communist sanctuaries may be the most overlooked or ignored subject by the media in its coverage of the war. International politics beginning at the United Nations set the groundwork for this war-winning communist asset. First, a little background.
The fact that North Vietnam was violating the neutrality of Cambodia and Laos was of no consequence to the U.S. Congress or the United Nations in the prohibition of American ground forces entering those “neutral” countries to eliminate the NVA base camp sanctuaries or to stop the communist infiltration into RVN.
North Vietnam had the ability to supply its invading army from sanctuaries and road networks (primarily the Ho Chi Minh Trail) through Laos and Cambodia with impunity from intervention and ground attack. Furthermore, North Vietnam received unlimited supplies from China, Soviet Union, Czechoslovakia, Cuba, North Korea, East Germany, and numerous other communist bloc countries through its ports including the North Vietnam’s giant Hai Phong harbor, and the Port of Sihanouk in Cambodia only a few miles from the South Vietnam border on the Gulf of Thailand.
The sanctuaries were not just a place for the communist forces to hide. The sanctuaries provided training and R&R for its soldiers, as well as resupply, reinforcements, medical care, operational headquarters, food storage, motorpools, fuel depots, communication networks, massive weapons and munitions storage facilities, and thousands of miles of roads comprising the Ho Chi Minh Trail network. And there was nothing the South Vietnamese, U.S., South Korean, Australian and NZ forces could “legally” do about it. The end result was that Allied forces could only fight the NVA when they caught them inside South Vietnam. In other words, the war had to be fought on terms dictated by the communists because of their ability to "hide" on the other side of the border.
Special Forces missions with Montagnard, Thai, and Cambodian mercenaries spied on and harassed the Ho Chi Minh trail network. The CIA and U.S. Air Force conducted their secret war in parts of Laos against overwhelming odds. As a Platoon Leader in early 1970, I witnessed cheers from my Blackhorse troopers on the Cambodia border as President Nixon’s secret B-52 bombing raids pounded NVA base camps just a few kilometers away on the Cambodian side of the Fishhook.
The 1970 joint ARVN-USA limited 60-day “incursion” into Cambodia had enormous success in terms of enemy supplies captured, and changed the course of the war in War Zones C and D, and in the Mekong Delta for nearly 18 months. It was the only official operation by U.S. ground forces to attack the communist sanctuaries during the course of the war.
Could an Allied military victory have been achieved without a ground invasion and without conquest of North Vietnam? Most likely "Yes" if the resupply of the communist forces was cut off through the following measures:
1) Ground interdiction of the Ho Chi Minh trail network in Laos and Cambodia to stop the flow of supplies.
2) Elimination of NVA base camp sanctuaries in Laos and Cambodia.
3) A naval blockade of military supplies arriving by ship in North Vietnam and Cambodia‘s Port of Sihanouk.
4) Continued bombing of military targets inside North Vietnam.
For example, the massive U.S. Linebacker II bombing campaign of North Vietnam and U.S. naval mining of the Hai Phong harbor quickly forced the NVA to sign the Paris Peace Agreement. However, because steps 1 and 2 above were not accomplished, the NVA quickly reverted to its old tactics after the U.S.A. forces withdrew and the POWs were freed.