When Col. Bui Tin of the North Vietnamese Army first trekked the Ho Chi Minh Trail in 1964 with a pack on his back, much of it was little more than a track wide enough for a bicycle. In succeeding trips as a correspondent for Hanoi's Army newspaper covering the war against the Americans, he watched it broaden and lengthen -- despite heavy U.S. bombing -- into a major route accommodating trucks, tanks and armored cars and dotted with repair workshops, arms caches, food and fuel depots and field hospitals.

During those years, thousands of Vietnamese were killed while building the trail into a legend: a network of 9,600 miles of main and branch roads -- 1,880 miles of them camouflaged -- over which hundreds of thousands of northern troops and countless tons of supplies flowed into South Vietnam.

Among the most important contributors to the Communist war effort, the builders of the Ho Chi Minh Trail are honored here at a remote cemetery in the middle of the Vietnamese panhandle just south of the former Demilitarized Zone.

Called the National Martyrs' Cemetery of Truong Son, the name of the mountain range through which the trail passes, this Vietnamese version of the Arlington National Cemetery covers nearly 40 acres near a branch of the trail and contains the graves of 10,306 men and women who died on it. First Arms Shipment Sent in 1959

Inaugurated in 1977 within view of the Truong Son range to the west, the cemetery also features monuments to the units that worked along the trail, such as the one in charge of refueling vehicles, now immortalized by a statue of a woman operating a gasoline pump.

Among those buried here, according to the cemetery's caretaker, Le Van Cau, are seven "heroes of the people's army" -- holders of Vietnam's highest military decoration -- and five "high-ranking officials."

One of the simple white tombstones also marks the grave of his elder brother, Le Ninh, who was killed in southern Laos in a 1972 U.S. air strike when he was 22, Cau said.

According to Bui Tin, a deputy editor of the Army newspaper Quan Doi Nhan Dan, thousands of others died on the trail over the years and remain buried elsewhere.

"There were a lot of losses -- from sensors, B52 bombing, Phantom jets and big fires," he said in Hanoi. "But the trail was never cut for more than two days."

The importance of the trail has been emphasized in postwar Vietnamese articles and books that also reveal some previously obscured facts about the war.

According to an account published in Hanoi's monthly Vietnam Courier in May 1984, the project to build "a special military communication line to send supplies to the revolution in the south and create conditions for its development" was launched in strict secrecy on May 19, 1959 -- the 69th birthday of then-president Ho Chi Minh.

Envisioned as "a special trail on which cadres, combatants, arms and medical supplies will be sent to the south," according to the instructions of Maj. Gen. Nguyen Van Vinh of the Communist Party Central Military Committee, the route was used to deliver the first northern arms shipment to guerrillas south of the 17th Parallel in August 1959, five years before the Tonkin Gulf Resolution paved the way for U.S. entry into the Vietnam War.

The postwar accounts thus make it clear that, contrary to Hanoi's persistent denials during the war that it was infiltrating men and arms into the south, North Vietnam was doing just that, and well before the first American combat troops arrived in 1965.

According to Lt. Col. Nguyen Thuong Dat, writing in the Vietnam Courier, the "Truong Son Strategic Supply Route," as the Communists called the Ho Chi Minh Trail, not only fueled the insurgency in South Vietnam but "played a decisive role in the supply of ammunition, food and medicines to the revolutionary armed forces" in Cambodia and Laos. In other words, it also helped Cambodia's brutal Khmer Rouge guerrillas come to power, before they were ousted by the Vietnamese invasion of Cambodia in December 1978.

Traffic on the trail increased in 1961 when a new route was laid on Laotian territory on the western side of the Truong Son range, and by early 1963 trucks were being used on some stretches, according to an account by Brig. Gen. Vo Bam.

Before motorized transport began in earnest on the trail in 1965, Communist troops carried supplies on their backs or on bicycles, sometimes performing extraordinary feats. The book "The Ho Chi Minh Trail," published in Hanoi in 1982, said one soldier, Nguyen Viet Sinh, carried a total of 55 tons over a distance of 24,615 miles during a four-year period. Massive Effort After Paris Agreement

Despite U.S. bombing that dropped 4 million tons of explosives on the trail during the war, according to Vietnamese estimates, the network was steadily improved and infiltration steadily rose. From an estimated 10,000 North Vietnamese troops in 1964, the number of regulars sent south climbed to more than 100,000 a year by 1966.

Then, after the 1973 Paris peace agreement, Hanoi ordered a massive effort to renovate two main axes of the trail, building steel and concrete bridges and metal surfaces wide enough to accommodate vehicles from tanks to missile carriers, the 1982 book said. By 1974, historian Dan Hong said, the tonnage transported on the trail was 22 times greater than in 1966 -- the peace agreement notwithstanding.

The trail played a key role when Hanoi launched its "Ho Chi Minh campaign" to take over South Vietnam in March 1975, beginning with a tank thrust into Ban Me Thuot in the central highlands. Thereafter, thousands of trucks streamed southward down the trail and down Highway 1 along the coast, culminating in the fall of Saigon on April 30, 1975. Wrote Dan Hong in his 1982 history: "The Ho Chi Minh Trail had finally led to Ho Chi Minh City." William Branigin