Vietnamese troops pressed their assault Saturday on the last major border stronghold of the Cambodian resistance, a battle that has drawn Thailand more deeply into the conflict.
For five straight days, a Vietnamese force estimated at 6,000 men has probed the defenses of the Tatum base of Prince Norodom Sihanouk's Cambodian guerrillas with infantry and pounded the cliff-top redoubt with artillery, though the shelling was reported to be lighter on Saturday.
According to Thai military officials, since the assault began at dawn Tuesday the Vietnamese strategy has been clear, and that strategy involves infringing upon Thai territory.
A frontal attack on the base, defended by an estimated 3,000 to 4,000 lightly armed guerrillas, presents difficult problems. The Tatum (pronounced TAH-toom) base stands just inside the Cambodian border atop a 1,200-foot-high escarpment. The Thai officers say that the Vietnamese have attempted to seize three hills in Thai territory on either side and to the rear of the base, an area of heavy undergrowth that provides concealment for attackers.
Gen. Arthit Kamlang-ek, supreme commander of the Thai armed forces, said that Vietnamese soldiers reached the tops of the two adjoining hills and were attacking the one to the rear on Tuesday before Thai artillery and an air strike drove them back. Arthit said Friday that the Vietnamese force trying to take the hills, estimated at 800 to 1,000 men, had been pushed out of Thai territory, but that he expected another attempt and that Thai forces would be ready for it.
The Thai commander also said he was confident that Tatum would not fall.
In this battle, more than any other in a dry-season offensive that has seen the Vietnamese overrun resistance camps along the length of the Thai-Cambodian border, the Thais find themselves a key to the defense of a guerrilla base.
The reported Vietnamese incursions on Thai territory around Tatum are the most serious in the five years of attacks on the border bases. Thai commanders say that they have reinforced their defenses in the area, evacuated more than 4,000 villagers in range of Vietnamese artillery and sought, and received, an acceleration of U.S. arms deliveries for the Thai military.
The Thai military says it will repulse any Vietnamese effort to use Thai territory in the campaign against the Cambodian resistance, a coalition of three groups including Sihanouk's force, the estimated 16,000 men of the Khmer People's National Liberation Front and the 30,000 to 40,000 guerrillas of the Khmer Rouge, the Communist organization driven from power in Cambodia by the Vietnamese invasion in December, 1978.
Thailand, its fellow members of the non-Communist Assn. of Southeast Asian Nations and the U.N. General Assembly recognize the coalition, under the titular leadership of Sihanouk, as the legitimate government of Cambodia. That is despite the country's domination by a 160,000-man Vietnamese occupation army and the Hanoi-installed government in the Cambodian capital of Phnom Penh.
But Thailand is the front-line state standing in support of the coalition guerrillas, whose supplies, mainly from China, traverse the border across Thai soil.
Southeast Asian diplomats say the Vietnamese appear determined to take all the resistance bases along the border in the current offensive. A Vietnamese defector interviewed near the besieged Sihanouk base said Friday that his commanders' orders were "to take Tatum at all costs."
Thai and guerrilla estimates of Vietnamese fatalities run as high as 300. Fewer than 20 Thai soldiers have been reported killed, along with several villagers caught in artillery exchanges.
With the advent of the rainy season in June, the combat situation has traditionally favored the lightly armed guerrillas, while the Vietnamese with their heavy weapons find the going harder as the Cambodian roads turn to mud. However, this year the Vietnamese have rolled up the resistance camps along the border and it remains to be seen whether the guerrillas can gain an advantage with their supply and communications lines disrupted.
And Thailand is faced with the reality--at present--of Vietnamese troops hard against the frontier.
For now, Thailand has taken a hard line. Foreign Minister Siddhi Savetsila has been quoted as saying "it is not possible to talk to (Vietnam) while they are attacking us."