EVERYBODY KNOWS HISTORY never repeats itself exactly. For a country like the United States, which is not enamored with the study of history, it may be futile to draw historical analogies, especially those relating to Vietnam.

But there is one so significant and so timely that our government might avoid critical errors by studying it. It relates to the extraordinary intelligence failure prior to the Vietcong's Tet offensive, and the confusion and politicization in the intelligence community in Washington, D.C., today.

In January 1966 the official U.S. intelligence estimate of the Vietcong order of battle was that there were 270,000 Vietcong guerrillas in South Vietnam. At the same time there had been approximately 50,000 to 150,000 Vietcong deserters, as well as 150,000 casualties each year. If these figures were correct, there were more deserters and casualties than the total number of enemy troops. Yet the war continued. Who was still fighting? Something was wrong.

In the Central Intelligence Agency, a young analyst named Sam Adams was assigned to study the Vietcong full time. After careful examination of numerous after-action reports and reports of enemy interrogations, Adams concluded that there were at least 200,000 more Vietcong fighters than were acknowledged in the U.S. assumptions. If Adams was right, the enemy force was at least twice as large as the U.S. assumed.

But Adams was virtually ignored. He continued to study the evidence, and by December 1966 he had concluded that there were 600,000 enemy soldiers.

There were conferences at which Adams presented his evidence, and at least one Pentagon analyst agreed with his conclusions. But the CIA and the military resisted changing the numbers, and so the official U.S. intelligence position was that our 350,000 soldiers were fighting only 270,000 Vietcong.

Gen. William Westmoreland was the commander of all U.S. forces in Vietnam. He returned to Washington in November 1967 and said, "The enemy is running out of men." Two months later, in January 1968, the Vietcong launched the Tet offensive with simultaneous attacks on numerous provincial capitals. U.S. troops repelled the attacks, but more than 10,000 of them died doing it. It was the greatest intelligence failure since Pearl Harbor.

The war continued and became increasingly costly and unpopular with the U.S. public. On April 30, 1975, the last remaining U.S. personnel escaped by helicopter from the roof of the U.S. embassy.

Seven years later, using Adams as a consultant, CBS News produced a documentary titled The Uncounted Enemy: A Vietnam Deception. It was broadcast nationwide on Jan. 23, 1982. It charged that there was "a conspiracy at the highest levels of American military intelligence to suppress and alter critical intelligence on the enemy in the year leading up to the Tet offensive."

Westmoreland filed a $120 million libel suit against CBS. After a trial lasting four and a half months, which produced volumes of testimony about how the records were distorted, Westmoreland negotiated a face-saving statement from CBS and dropped his suit.

This should force the U.S. press and the public to ask a lot of questions today. What is the Iraqi enemy order of battle? In Vietnam, Adams found there were categories of Vietcong fighters that weren't being counted at all. One group the Vietcong called "assault youths," weren't even on the order of battle. Are we making similar omissions today? Does the Pentagon really know whom we are fighting and what their numbers are? Is there a Sam Adams somewhere in the intelligence community who is trying to do an honest job of figuring this out?

Adams, a direct descendant of the great Adams family of colonial Massachusetts, died of a heart attack in October 1988 at the age of 55. George Tenet, the director of the CIA, told President George W. Bush that the existence of weapons of mass destruction in Iraq was an intelligence "slam dunk." He was awarded the Presidential Medal of Freedom.

Marshall Windmiller is professor emeritus of international relations at San Francisco State University.