OF ALL THE intelligence from Hiroshima coming back to him on the island of Tinian on Aug. 6, 1945 and after, one ominous note "upset and puzzled" Dr. Norman F. Ramsey. Tokyo Rose, the English-speaking propagandist, announced over the radio from Japan that radiation was causing widespread death and injury to survivors of the initial atomic blast that destroyed much of Hiroshima.

This report came as "quite a surprise" to Ramsey, the personal representative of J. Robert Oppenheimer -- director of the laboratory where the first atom bomb was made. In all the discussions among scientists who had worked on the wartime crash program to build an atom bomb, no one had predicted radiation problems. The bomb had evidently done something that no one had expected.

Indeed, when Ramsey relayed the reports of radiation deahs and illnesses, his scientific superiors and their military bosses dismissed the information as "hoax or propaganda" because it "did not correspond to any experience known here."

In the months and years that followed, Ramsey, other scientists, public officials and eventually the public learned a great deal about the lethal long-term radiation effects of "the bomb." Equally important, we are now beginning to learn just how little the scientists and the politicians knew about the bomb when decisions were made to use it.

The ignorance of both scientists and politicians, and their unwillingness at the time to take steps to learn more, led to drastic consequences we still live with. We can't rewrite history, but President Reagan's so-called "Star Wars" proposal to build superweapons in space to shoot down ballistic missiles again raises the possibility of unanticipated but potentially disastrous consequences.

The connection between the decision to make and drop the first bomb and Reagan's proposal to transfer the arms race to space was first noted in 1983 by Edward Teller, the godfather of the star wars idea and father of the H-bomb.

Writing in The New York Times shortly after Reagan made his proposal, an elated Teller said he was reminded of "another . . . turning point in world history" -- the day in 1939 when he and a handful of proud scientists persuaded President Franklin D. Roosevelt to plunge ahead with the scientific research that ultimately produced the nuclear crisis of the present day: the Manhattan project to build an atomic bomb.

The parallel is apt, but not quite in the way that Teller sees it. Now as then, on the threshhold of these technological departures, scientists and politicians cannot begin to fathom what the new technology may actually produce. Yet the push is on again to escalate warfare, this time to invade the heavens, again with unknown consequences. Today, Teller and his fellow-enthusiasts do not know what new tragedies their wars in the heavens might visit upon civilization. Back in 1939, the scientists had no idea, to cite one example, that they had invented a new dimension of warfare: nuclear radiation that would kill, maim and poison on a vast scale.

Scientists, soldiers and politicians did not know what the bomb really was. Then as now, the worst enemy of good decision-making was ignorance.

One thing is different today: The price of uninformed discussion has turned prohibitive. Before Hiroshima, we could not destroy ourselves. Since Hiroshima, we can. The stakes have changed. No longer will we be doomed to repeat the errors of the past if we don't learn from them. We probably won't be here to repeat them.

It is quite literally true that the radiation dimension of the A-bomb was unsuspected. Four of the principal scientists who worked on the performance estimates of the bomb in Los Alamos, N.M., during World War II recently told me so, including Hans A. Bethe, the head of the theoretical physics division.

Oppenheimer, their revered director, who was responsible for solving what he called the "technically sweet problem" of the first nuclear weapon, had reassured his team: the bomb, he said, would be just another conventional weapon except that it would make a "very big bang." This uninformed judgment prompted the scientists to plan for the dropping of 50 A-bombs on Japan, not just the two that were released on Hiroshima and Nagasaki in August 1945.

The reports about radiation were dismissed because scientists knew so little about it. That is: doctors had been aware since the 1890s that too much radiation damaged people. But what was too much? And how long can it take for damage to manifest itself or cause death? These questions are still not totally understood by physicians, including the doctors I lately visited in the 170-bed "A- Bomb Hospital" in Hiroshima where A-bomb victims are still dying 39 years after their exposure to what had been dismissed as a "hoax."

Had the scientists and politicians been able to fathom the depths of their ignorance, they might have seriously considered -- as they did not -- the option to demonstrate the bomb to the Japanese or an international group before its use in combat. A demonstration of the bomb's potential not only was ignored but was very deliberately sabotaged. Hundreds of thousands of lives might have been saved and even more might have been spared the agony of what amounted to an uncontrolled experiment on human subjects.

More important for purposes of the present, however, is that we realize that scientists and politicians deliberately decided not to inform themselves fully about a new weapon before using it. (Contrary to what most people believe, the test at Alamagordo, N.M., was a ground explosion of bomb components for a plutonium weapon, not of an assembled A-bomb from the air; the Hiroshima bombing the following month used an untested uranium weapon.)

One senior scientist after another tried to sell Oppenheimer on a variety of ways to make a demonstration persuasive. Since the subject, as Ramsey said was not "saleable," the suggestions for a demonstration were vague. Nobody even recommended testing the bomb on large laboratory animals. So, Oppenheimer had no difficulty turning the doubters away, one by one, without serious analysis. When one of his most trusted men came to speak up for this alternative for the third time, "Oppie" shut him off by declaring his trust in the military. They would know what to do.

Oppenheimer chaired a final all- weekend meeting at Los Alamos of his science high command: Ernest O. Lawrence, Arthur H. Compton and Enrico Fermi, all Nobel Prize winners. The meeting was so secret that even Oppenheimer's friends did not know it was taking place. All three of Oppenheimer's peers favored a demonstration. Fermi argued fiercely for it through the last night, not giving up until 5 a.m.

Yet Oppenheimer deliberately failed to inform Washington even that a disagreement existed, and when 67 senior scientists at the other principal atomic headquarters, the University of Chicago, formally petitioned President Truman for a demonstration, the military carefully channelled the document from echelon to echelon until the officers could be certain that the presidential decision to drop the bomb was sealed. Then the petition was tucked into a file.

Neither the president nor his secretary of war, Henry L. Stimson, ever saw the plea from Chicago or heard of the interest in the demonstration idea that prevailed among Oppenheimer's senior scientists and his high command. It was a classic coverup engineered by Oppenheimer and his military boss, the commander of the war-time Manhattan Project, General Leslie R. Groves.

Only once did the demonstration option receive top level attention of a sort. At an all-day Pentagon meeting chaired by Stimson on May 31, 1945, the idea, which was not even on the agenda, was bandied about for 10 minutes, somewhat like office gossip, during the luncheon break.

How can clever leaders arrive at such decisions within a vacuum induced by ignorance and sabotage, a fatal mindset that blinds them to alternatives?

There are at least three answers to that complicated question:

Failure of military intelligence. Just as, years later, it turned out that no "missile gap" existed, no real nuclear "race" with the Germans took place in World War II. Roosevelt was sold on the A-bomb because the Nazis were building it and, later, were believed to be ahead. Not until the end of the war did an intelligence mission discover that the Germans had run aground in the pre-kindergarten stage of nuclear research. We had gone ahead with the nuclear "competition" on the basis of a non-existent premise.

Hatred of the enemy. Then as now, we faced what our leaders perceived as an "evil empire." The Japanese had committed outrageous atrocities against American prisoners of war. Hatred against them ran at fever pitch. Oppenheimer's senior adviser, I. I. Rabi, told me that it would have been stupid wishful thinking to expect the politically minded Truman not to rain destruction on the "orientals." "They were not people one loves," said Rabi.

Sheer momentum. The record shows that the World War II bomb- builders and decision-makers, having spent $2 billion pre-inflation dollars and having triumphed over countless technical crises, were powerfully motivated to drop the bomb -- simply to justify the manpower and money invested.They decided on its use -- as Arthur Schlesinger much later described the planning of the Bay of Pigs invasion disaster -- "in an air of assumed consensus."

The decisions were made in ignorance, but even when the implications of the Hiroshima and Nagasaki blasts began to be known to policy-makers, they tried to suppress the information. U. S. occupation authorities refused to let even Japanese medical journals discuss radiation disease, and the epidemic of lingering after-effects (leukemia increased to 50 times the normal rate) did not hit with full force until the 1950s. Even today, some U.S. "experts" maintain a see- no-evil resistance against the facts, claiming that "1,000 or 2,000 people" suffered radiation injuries in Hiroshima and Nagasaki. But American physicians of the U.S. Atomic Bomb Casualty Commission estimate that 20,000 were killed by radiation in Hiroshima alone; another 20,000 were significantly injured, and the actual numbers, they concede, will never be known and may have been twice as high.

Excessive secrecy fed the blind decision-making, not only vis the public but within the nuclear weapon project. The Oak Ridge, Tenn., bomb laboratory was in danger of blowing itself up because it was not permitted access to technical information available at its sister laboratory in Los Alamos.

Secrecy and suppression of information about radiation continued after the war. One victim of this policy was Dr. Stafford Warren, the chief medical officer of the Manhattan Project and of the first postwar nuclear tests in the Pacific. On January 19, 1947, the doctor spelled out his nightmare in a top-secret memorandum to his superior officer. He recalled how wartime estimates of radiation tolerances had been "extrapolations" and "guesses" that had been "wrong by large and dangerous amounts." When the doctor returned to civilian life as professor at the University of Rochester School of Medicine, he felt it was time to inform the public.

He drafted a speech concluding: "Inhabited areas so contaminated would have to be abandoned. This and all the rest that goes with it makes war intolerable." In a memorandum to Groves, the doctor requested permission to deliver his talk at a series of meetings beginning with 200 medical students at the Massachusetts General Hospital. For Groves, Warren's threat to nuclear tranquility was intolerable. He denied the required clearance at once by phone.

Perhaps most significantly, Warren's travail did not surface until 1983, two years following his death, when the relevant papers were discovered in the library of the University of California at Los Angeles, where he had been dean of the medical school.

Given this web of internal controls, manipulations and worse, public insight into the genesis of our nuclear crisis varies from sparse to nil. Public debate lacks a factual underpinning. How did we slide into today's stalemate? The explanation has been mostly rhetoric, and, as Herbert York, the former director of the Lawrence Livermore Laboratory, wrote, "the rhetoric hasn't changed in 35 years." It is as if the debate about star wars schemes and the redundancy of more and more missiles, on the one hand, and steps toward disarmament on the other, represent course subjects that might be called Nuclear Arms 103 and 104, while courses in Nuclear Arms 101 and 102 have never been given.

And the decision-making of the 1980s remains under the spell of the prophet of 1939. In 1982, Edward Teller assured the huge readership of The Reader's Digest that the dangers of nuclear radiation are largely "myths" and that the streetcars in Hiroshima started running three days after the A-bomb fell (In fact, it took three months before a few streetcars and buses were again operating.) This distortion offers a grotesquely misleading picture of the destruction caused by the Hiroshima bomb, a relatively minuscule model by standards of today's weaponry.

Teller's voice remains influential. Reagan has consulted with him for years. And the president's science adviser, George A. Keyworth II, a physicist who spent six years at the Los Alamos laboratory a decade ago and who is an enthusiastic promoter of space-based weapons, is a Teller disciple. The father of the H-bomb recommended Keyworth for the White House post.

We still have time. When Congress next considers appropriations for star wars, it could call hearings into the Hiroshima decision and the role of science in momentous military turning points. Let the scientists of World War II speak out with their informed regrets. Their hindsight could bring us foresight.