Vietnam Moves to Crush an Elusive Foe : Cambodian Rebels, Disrupted and Exiled to Thailand, Able to Fight On

BANGKOK, Thailand — Three months into its dry-season offensive against Cambodian guerrillas, the Vietnamese army is trying to consolidate its victory over an enemy that is no longer there.

Vietnam is also attempting to seal the Thai-Cambodian border. Cambodian civilians, drafted from villages and towns in the interior, have renewed work begun two years ago on a security barrier, a trench about 15 yards wide on the Cambodian side of the Thai frontier, according to Prasong Soonsiri, the head of Thailand’s National Security Council.

The trench is being mined, Prasong said in an interview, with the intention of disrupting supply and communication lines between the Cambodian resistance forces and their supporters, who have been driven to the sanctuary of Thai soil.

Prasong said the Vietnamese are trying to isolate the resistance units from their sources of supply and then attack them in search-and-destroy missions.

He and foreign diplomats here predict that the effort will fail. The Thai-Cambodian border stretches for nearly 500 miles, much of it in rugged terrain that the guerrillas know well. The Vietnamese security ditch, paralleling the border northward from a point east of the Cambodian town of Poipet, will cover a distance somewhere between 12 and 18 miles, just a fraction of the frontier.

Furthermore, the resistance, in anticipation of a major Vietnamese push in this dry season, has cached arms in the Cambodian interior, Prasong said. And, according to Western diplomats as well as the Thai official, arms will continue to move across the border.

Although the Vietnamese offensive has not crushed the resistance, it has achieved a secondary aim, a Western diplomat said, “knocking it off balance and disrupting infiltration routes into the interior.”

But the guerrillas, particularly the seasoned Khmer Rouge Communists, have fought in the border region for years and are expected to be able to keep open the present supply lines or establish new ones.

Weapons From China

It is an open secret, diplomats say, that most arms and other supplies for the Cambodian guerrillas are provided by China, shipped to a Thai port and moved secretly to the border. Some members of the Assn. of Southeast Asian Nations, a regional organization of non-Communist countries, are also reported to be providing arms, along with other aid.

The guerrillas are nominally united as the coalition government of Democratic Kampuchea, which holds the country’s seat in the United Nations. Its president is Prince Norodom Sihanouk--the Cambodian leader under a variety of titles from 1941 to 1970, who commands a guerrilla force estimated at 9,000 men.

The two other members of the coalition are the non-Communist Khmer People’s National Liberation Front, headed by former Prime Minister Son Sann, with an estimated 16,000 troops, and the Khmer Rouge, with 35,000 to 40,000 guerrillas, the best-armed, best-trained and most experienced of the three factions.

Son Sann carries the title of coalition prime minister, and the vice president is Khieu Samphan, a longtime power in the Khmer Rouge, which ruled Cambodia in brutal fashion from the spring of 1975 until driven from power by the Vietnamese invasion of December, 1978.

The Vietnamese have an army estimated at 160,000 to 180,000 men in Cambodia, supplemented by two divisions from Vietnam for the current offensive. The Vietnamese-installed government in Phnom Penh, headed by Heng Samrin, has an estimated 30,000 men under arms.

Diplomatic Push, Too

The resistance forces were particularly active on the diplomatic and military fronts in 1984, and the Vietnamese unleashed their strongest dry-season offensive yet against the resistance border positions beginning last November.

“They put four to five times as much manpower, artillery and other heavy weapons into this offensive” compared to previous dry-season campaigns, the Western diplomat said.

Prasong, the Thai security chief, said Vietnam sent seven of its divisions--about 60,000 men--into battle, using 105-, 130- and 155-millimeter artillery, Soviet-made tanks and highly effective MI-24 helicopter gunships, which the Soviets have used against the Muslim insurgents in Afghanistan.

The Vietnamese struck first against the border bases of the Khmer People’s National Liberation Front--using superior firepower to take the headquarters encampments, capture some weapons and drive the front’s supporters and some guerrillas across the border into Thailand.

After their December and January assaults on the front’s bases at Nong Samet and Ampil, the Vietnamese struck farther south early in February, pushing the Khmer Rouge fighters out of their redoubts in the mountainous Phnom Malai region and inside Cambodia south of the Thai border town of Aranyaprathet.

The base for Sihanouk’s forces at Tatum in the north has escaped attack so far.

Refugees Flood Across

Meanwhile, the fighting has increased the population of Cambodian refugee camps on the Thai side of the border. By the end of February, there were 240,000 Cambodians in the camps, a U.N. relief official said.

The Thais insist that no guerrillas can enter Thailand and that they confiscate any arms carried by the refugees. But it is a long border.

Although the Vietnamese have taken ground and led some coalition leaders to make embarrassing admissions of “strategic retreats,” Western and Thai officials say the resistance is still a fighting force.

The Khmer Rouge broke away from the onslaught and filtered into the Cambodian interior in small units, the officials say, and Son Sann’s forces have retaken some of the territory lost early in the offensive.

The key question here is whether these Khmer Liberation Front forces are prepared to follow the Khmer Rouge strategy and carry on guerrilla campaigns deep inside Cambodia, where the important struggle for control of the country will take place. Previously, the front’s command has operated out of border bases where their families and civilian supporters were encamped.

Prasong said that resistance forces placed 60,000 land mines along the routes of the Vietnamese advance, adding to those already planted in the border region by all sides. Bangkok newspapers regularly carry photographs of one-legged refugees moving along the border, testament to the danger of mines.

Vietnamese Morale Weakened

The Vietnamese, apparently worried about the vulnerability of their extended supply lines, have pulled some troops back from the border, Prasong said. He estimated their forces along the frontier at 20,000 to 25,000. The Thai security official also questioned their morale.

“In every area that they overrun . . . they see only their friends killed,” he said, “but it is difficult to see the Khmer (guerrilla) body.”

He said that about 200 Vietnamese soldiers have deserted. Most were draftees from southern Vietnam, he said, and they questioned why they should have to fight in Cambodia.

The Western diplomat added, “The resistance can’t drive the Vietnamese out of Cambodia, but it’s a constant reminder to Hanoi that this could go on for a long time--that perhaps they should seek a settlement.”

However, with the results of the dry-season fighting still indefinite, neither side is emphasizing a diplomatic solution.