SAIGON — Fewer than 200 U.S. defenders, backed by massive air support, blasted apart a Red battalion as it tried to overrun their tiny patrol base near the Cambodian border, military spokesmen reported Saturday.

The Red battalion swept out of its Cambodian sanctuary 35 miles west-northwest of Saigon early Saturday in the wake of a rocket barrage to attack Diamond II, a patrol base manned by troops from the U.S. 25th Inf. Div. and two howitzer gun crews.

Trying to use the cloudblanketed darkness as cover, the Reds pushed toward the perimeter firing machine guns, rocket grenades and automatic rifles. The two U.S. howitzer crews lowered their weapons like rifles, using beehive rounds and a meat grinder of infantry rifle fire that chopped the Red ranks before they reached the base defenses.

With the Communists held back U. S. Air Force warplanes and "Spooky" gunships ripped in at ground level, forcing the Reds to break into small groups and run for Cambodia.

A sweep of the pock-marked battlefield at dawn produced 81 enemy dead. U.S. losses were four killed and 13 wounded.

Spokesmen said the patrol base bordered on an area called the "Angel's Wing" and was less than a mile from where Red battalions tried to overrun Diamond I. during the first three days of the current offensive. Some military leaders believe the entire combat-hardened 9th NVA Div. is massed along the Angel's Wing ready for intermittent thrusts into South Vietnam toward Saigon.

U.S. officers said Maj. Gen. Ellis Williamson, commander of the 25th Division, "agitated" the Communists by setting up an artillery and patrol base just across from its so-called Angel's Wing sanctuary in Cambodia, the Associated Press reported.

Less than 24 hours later, the battalion of' 640 North Vietnamese, camouflaged with rice straw on their backs, launched their assault behind a heavy mortar barrage. But the Americans were waiting.

"They began sneaking across the rice paddies," a 25th Div. officer said. "We picked them up on radar before they even got close."

A 25th Div. listening post of about a dozen men set out in hedgerows 200 yards from the U.S firebase also picked up the Communist movements, the AP said.

The North Vietnamese troops bypassed the small patrol and went for the bigger base instead.

"There were North Vietnamese soldiers up and running toward the firebase," said Spec 4 Robert Odom, one of the men on the listening post. "It looked like a football team's end-around."

As the Communist troops got to within 30 yards of the firebase, two 105mm howitzers lowered their barrels and opened fire with shells containing thousands of pieces of deadly shrapnel, AP said.

Odom said that under the artillery bombardment and withering machine gun fire from helicopter gunships, the Communist troops turned and fled.

"We picked more of them off as they came running back across the rice paddies," said Odom. He said some of the retreating soldiers were carrying wounded with them. One badly wounded prisoner was captured and may need to have a leg amputated, he added.