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1970 - Cambodian Incursion

Bases outside South Vietnam had been strictly off limits to allied ground forces. This rankled U.S. commanders, who regarded the restriction as a potentially fatal mistake. By harboring enemy forces, command facilities, and logistical depots, Cambodian and Laotian bases threatened all the progress the allies had made in the South since Tet 1968. To the Nixon administration, Abrams' desire to attack the Communist sanctuaries had the special appeal of gaining more time for Vietnamization. With most U.S. combat units slated to leave South Vietnam during 1970 and 1971, time was a critical factor for the success of Vietnamization and pacification. Neither program could thrive if South Vietnam's forces were distracted by enemy offensives launched from bases in Cambodia or Laos. Because of the proximity of the Cambodian bases to Saigon, they received first priority. In early 1970 Cambodia's neutralist leader, Prince Norodom Sihanouk, was overthrown by his pro-Western Defense Minister, General Lon Nol. Nol closed the port of Sihanoukville to supplies destined for Communist forces in the border bases and in South Vietnam. He also demanded that Communist forces leave Cambodia and accepted the South Vietnamese government's offer to apply pressure against those located near the border. (A year earlier American B-52 bombers had begun in secret to bomb enemy bases in Cambodia.) The mood in the Oval Office just before the Cambodian "incursion" at the end of April 1970 bordered on the desperate. A joint American/GVN move against the supposed headquarters of the NLF/North Vietnamese would serve two purposes, then: protect Lon Nol and demonstrate that Vietnamization really was working. Nixon expected trouble with the antiwar movement and "up on the Hill," but the risks seemed worth it. On television, he told the nation that the operation would strike at the "heart of the trouble." It "puts the leaders of North Vietnam on notice that . . . we will not be humiliated. We will not be defeated."

By mid-April 1970 South Vietnamese armored cavalry and ranger units, with no U.S. advisers accompanying them, were mounting large-scale operations across the border from III Corps and uncovering large caches of enemy supplies and equipment. The main assault began on the twenty-ninth. That morning three South Vietnamese task forces, this time with a full complement of U.S. advisers, and preceded by heavy air and artillery attacks, launched Operation TOAN THANG 42, knifing into Cambodia's Svay Rieng Province and pushing through enemy resistance. Two days later, on May 1, units of the 1st Cavalry Division; 25th Infantry Division; 3d Brigade, 9th Infantry Division; 11th Armored Cavalry Regiment (ACR); and South Vietnamese 3d Airborne Brigade, under the command of Brig. Gen. Robert L. Shoemaker, followed from slightly to the north. The 4th Infantry Division attacked from II Corps four days later.

Cambodia became a new battlefield of the Vietnam War. By May 2 South Vietnamese forces had cut off the Parrot's Beak, an area that jutted into South Vietnam near the III Corps-IV Corps border, and U.S. and South Vietnamese troops had linked up near Memot in the so-called Fishhook, meeting little opposition from enemy security forces. Snuol, a large enemy logistical hub, fell to the tanks of the 11th ACR three days later. In the weeks that followed the allies cut a broad swath through the enemy's sanctuary and uncovered storage sites, training camps, and hospitals far larger and more complex than anyone had anticipated. One site in the Fishhook, dubbed "the city" in deference to its size, covered three square kilometers and contained mess halls, a livestock farm, supply issuing and receiving stations, and over two hundred caches of weapons and other materiel, most of it new. By one estimate, the allies in Cambodia seized enough weapons and ammunition to arm fifty-five battalions of main-force infantry. Main-force offensives against South Vietnam's III and IV Corps were derailed for at least a year.

However, the allies did not find large enemy forces or the COSVN headquarters. Only relatively small delaying forces offered resistance, while main-force units retreated deeper into Cambodia. Meanwhile, the expansion of the war produced violent demonstrations in the United States. In response to the public outcry Nixon imposed geographical and time limits on operations in Cambodia, which enabled the enemy to stay beyond reach. At the end of June, one day short of the sixty days allotted to the operation, all advisers accompanying the South Vietnamese and all U.S. Army units had left Cambodia.

Political and military events in Cambodia triggered changes in the war as profound as those the Tet offensive had engendered. From a quiescent sideshow of the war, Cambodia became an arena for the major belligerents. Military activity increased in northern Cambodia and southern Laos as North Vietnam established new infiltration routes and bases to replace those lost during the incursion. North Vietnam made clear that it regarded all Indochina as a single theater of operations. Cambodia itself was engulfed in a civil war.

As U.S. Army units withdrew, the South Vietnamese Army found itself in a race against Communist forces to secure the Cambodian capital of Phnom Penh. Americans provided South Vietnam's overextended forces air and logistical support to enable them to stabilize the situation there. The time to strengthen Vietnamization gained by the incursion now had to be weighed in the balance against the South Vietnamese Army's new commitment in Cambodia. To the extent that South Vietnam's forces bolstered Lon Nol's regime, they were unable to contribute to pacification and rural security in their own country. Moreover, the South Vietnamese performance in Cambodia was mixed. When working closely with American advisers, the army acquitted itself well; though there were flaws in planning and the use of air and artillery support. The South Vietnamese logistical system, with a few exceptions, proved adequate. The difficulty was that the North Vietnamese Army largely chose not to fight, so the South Vietnamese Army was never really tested. Furthermore, the South Vietnamese command had relied on rangers, armored cavalry, and airborne troops-elite units-bypassing the mediocre infantry divisions hampered by their politics. If the elite units performed credibly, the shortcomings in the regular army remained intact, starting with poor leadership and lack of discipline.

The explosion Nixon set off with the Cambodian "incursion" reverberated across the political landscape from Congress to Kent State University and back to the Lincoln Memorial, where Nixon tried to start a pre-dawn dialogue with college students from all parts of the country. Whatever time the incursion may have bought for Saigon, it did not do anything to improve Lon Nol's chances for surviving. A special National Intelligence Estimate in early August 1970 reported that in the four months since Sihanouk's ouster, half of Cambodia had been overrun by the Communists. Without outside support in the form of heavy military assistance, the outlook was grim. He might survive until the end of the year, until the rainy season ended, but after that the Cambodians were in for it, with the prospect for heavy fighting against long odds.

Hanoi would have to judge above all how the Cambodian situation would affect the will of the US to prosecute the struggle in Vietnam. The tone of this conclusion was very different from the pre-incursion Estimate as it reverted to the "test of wills" theme. Hanoi had never doubted the superior physical and material capabilities of the US, it asserted-without saying how those capabilities could have been used differently from Rolling Thunder to Cambodia-while North Vietnam's hopes had lain in its ability to out-stay the US "in a prolonged politico-military contest carried on according to the principles of revolutionary struggle." The public outcry against "the Cambodian adventure" might lead Hanoi to believe it had the upper hand now. Dean Rusk never said it better. "But it [Hanoi] must recognize that the contest in Indochina will continue for some time."

Calling the incursion, "the Cambodian adventure," was something of a give-away, even if not precisely intended in that way by the August 1970 Special NIE. At the least it suggested Nixon's rash effort to test Vietnamization had made things worse, politically at home and militarily in Cambodia. In April 1971 a new NIE foresaw little change in the "reasonably good" outlook for Vietnam for that year but thought an enemy offensive was likely the following year when the US election season opened and the troop drawdowns continued. South Vietnam would continue to require substantial US support. It took note of serious problems in ARVN morale, while Hanoi's advantage was still the "apparent durability of the communist party apparatus." Besides the communist threat, moreover, the GVN faced other internal problems that might well produce tensions, growing anti-Americanism, and a government relying solely on coercive powers. Should that happen, the outlook would change to one of increasing instability "risking political disintegration."



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