SAIGON -- The Communist High Command in Vietnam knew a year ago that its main forces had been defeated and was preparing for a return to guerrilla warfare, a captured Communist document has revealed.

The highly-classified document is COSVN (Central Office for South Vietnam) Resolution 14, captured by Allied troops earlier this year and made public by U.S. officials Tuesday.

Even as North Vietnamese Premier Pham Van Dong last October was wishing success to "our American friends" on their "moratorium day," COSVN big-wigs were drafting the remarkable resolution, which is a single breath claims victory and admits defeat in backhanded Communist jargon.

Stamped "absolute secret" (roughly equivalent to U.S. "top secret"), the resolution said in effect that the war by main force units has been lost and that the Communists must start over again at the guerrilla warfare level, the first stage in Communist "wars of liberation."

The resolution blamed local party branches for failing to conscript enough troops and for failing to popularize "armed struggle among the masses."

"As a consequence, the guerrillas, forced to operate in isolation, were unable to profit from the strength of the masses ..." the document said. Translation: The people wouldn't help the Red soldiers.

Because of this, the resolution says, " ... the enemy, confronted with the most serious defeats, reacted by intensifying his military attacks and pacification operations to protect his rear areas, and to encroach on liberated areas."

The only way to cope with such an enemy, the document advises, is by guerrilla warfare to wear down and destroy the enemy "on a continuing basis," compel him to stretch his troops thin until his fighting stamina degenerates and his morale and organization collapse.

After several pages of analysis of the military situation, much of it rationalizing the failure of the Communistís main force campaigns, the resolution states simply:

"One of our weaknesses is the lack of revolutionary bases."

There follow detailed instructions for building a guerrilla organization from scratch and coordinating it with party activity.

"Guerrilla organization must be secret and may consist of three-to-five-man cells," branches are told. "The cell members should be able to live among people in hamlets and cities."

Their primary mission is to attack village officials, police, pacification cadre and uniformed military personnel, the resolution says.

Persons living near American or Vietnamese bases, communication axes, supply depots, ports, training centers and the like are instructed to plan attacks on them.

The resolution blames the Communist failure on the lack of continuing effort to build guerrilla forces after main force units joined the fight.

"Because we failed to persevere in ... developing guerrilla warfare in cities and populated areas, especially at a time when the enemy is intensifying his attacks and pacification operations more ferociously, ... we were not able to ... create a strength which would change the balance of forces between us and the enemy," the document concedes.