AMONG THE THOUSANDS who came here last week for the American Gathering of Jewish Holocaust Survivors were some who likely would have been killed by the United States had America heeded pleas to bomb Birkenau, the largest of six Nazi death factories in Poland and one of the three camps that comprised Auschwitz.

But many more might have lived had we bombed Birkenau's four gas chambers and crematoria, designed to burn 10,000 bodies a day, and the rail system that fed them. Was bombing feasible? Birkenau was fewer than five miles west of Buna, a synthetic fuel plant that had already been targeted for repeated air strikes.

Until now, such calculations on the abacus of genocide have not been met head-on, and in detail, by John J. McCloy, the only living person who had a major role in opposing the bombing pleas.

McCloy -- who at the time was assistant secretary of war, with responsibility for contacts between our armed forces and civilian populations -- recently talked at length about the refusal to bomb Auschwitz, first in a phone conversation, then for 11/2 hours in his Wall Street law office. Alert and vigorous at 88, he said the issue was not "much of an episode in my life" in the War Department, which kept him as busy as "a one-armed paperhanger."

But his version of events turned out to be, in several critical respects, unsupported or disputed by historians and official records. For example, McCloy attributes a key role in the non-bombing of Auschwitz to the late Gen. Henry H. (Hap) Arnold, commander of U.S. Army Air Forces. This startles retired Air Force historian Murray Green, who researched Arnold's career for 10 years. "I don't even believe (the issue) came to Arnold," he says. The available evidence suggests that McCloy "is manufacturing a discussion."

McCloy cannot recall exactly when Gen. Arnold gave his advice against the death- camp bombing, or whether the conversation was directly with Arnold or through an aide. "I'm sure I talked to Arnold about it," he says, but added that he couldn't state "definitely" that this was the case. Nonetheless, McCloy says, he heard from Arnold, among other things, of "an understanding with the British" under which the United States probably needed their "permission" for a Birkenau bombing.

Green questions the plausibility of this account as well, saying, "In no sense did Arnold clear bombing missions with the British."

He also says that had bombing been posed to Arnold as an operational question, the general would have told two superiors with whom he was in almost constant contact: the late Gen. George C. Marshall, a close friend who, as chief of staff, was his boss, and Robert A. Lovett, the assistant secretary of war for air whose office was next to Arnold's.

Marshall biographer Forrest C. Pogue said, "I've never run into information that anyone ever brought this to Marshall or to anyone near his level." Lovett said that he could not recall the possibility of bombings being referred to him.

McCloy, who has been an adviser to presidents as well as chairman of Chase Manhattan Bank, the Ford Foundation and the Council on Foreign Relations, has turned down other interview requests, notably one from Prof. David S. Wyman of the University of Massachussetts at Amherst, a leading authority on the U.S. response to the Holocaust. But he indicated he had been goaded to speak out by Harvard historian Alan Brinkley, who claimed in the February Harper's that the non-bombing and the wartime internment of Japanese-Americans (in which McCloy was also a central figure) have "haunted" him and "the American conscience."

The article "sent me up the wall a little bit," McCloy volunteered. "I wasn't haunted (by the non-bombing), because I didn't have a damn thing to do with (it)," he said. "I didn't have any decision to make."

"The president (Franklin D. Roosevelt) could do it," McCloy continued. "No one else could. . . . If the president wanted to do it, all he needed to do was press a button. I couldn't order a soldier from 'A' to 'B'. . . . I didn't oppose it. I just passed on (FDR's decision)." He said he had "never talked" about the issue with FDR.

What of the "scandal" label pinned on the non-bombing by columnist George Will? "No, I don't think it was a scandal," McCloy said. "I haven't anything on my conscience. . . . I know my conscience is perfectly clear."

What of the claim in a 1978 Commonweal article that "Had Auschwitz's victims been predominantly Englishmen, and probably gentiles of any nationality, powerful Americans would have urged bombing -- and the government would have taken heed?"

"I don't think it was relevant (that most of the victims were Jews)," McCloy said. "Not a bit." As evidence of his sympathy for the Jewish tragedy, he stressed his "massive" effort to persuade the late Chancellor Konrad Adenauer to increase West Germany's reparations to Israel. "I importuned Adenauer on a number of different occasions, and he upped the ante four times," he said.

Nearly four decades after World War II, almost any account of a decision that was not central to the all-consuming goal of victory may offer light but not a full and final answer. That one will never emerge is suggested by historian Wyman's experience after a dozen years' research. To this day, he is unable to prove his belief that the War Department's Operations Division (general staff) "balked" at bombing because it did not want such an extra burden while fighting a war.

A prime case in point involves a claim made repeatedly by the War Department: Birkenau could be attacked by B17 and B24 heavy bombers only from distant British bases. McCloy himself made that claim on Nov. 18, 1944, in rejecting a strong appeal by John W. Pehle, executive director of the War Refugee Board, to bomb the gas chambers and crematoria.

Repeating a passage in a draft memo from the Operations Division for Assistant Chief of Staff J.E. Hull, McCloy said: "Use of heavy bombardment from United Kingdom bases would necessitate a round trip flight unescorted of approximately 2,000 miles over enemy territory." His memo also reflected Hull's view that "the proposal is of very doubtful feasibility and is unacceptable from a military standpoint at this time in that it would be a diversion from our strategic bombing effort and the results obtained would not justify the high losses likely to result from such a mission."

Today, similarly, McCloy says that Gen. Arnold had opposed such "deep penetration" strikes, saying they would entail sending 35 to 50 B17 or B24 heavy bombers on special missions too long to allow fighter escorts throughout, bring "very heavy casualties" to U.S. airmen, kill inmates while inciting Nazi "reprisals" against them, and still be ineffective.

But neither in 1944 nor in 1983 did McCloy (or Hull) hint at -- if they knew -- a revealing fact that became widely known in 1978: For six months, the U.S. 15th Air Force, based not in England but at Foggia in southern Italy, had been regularly demonstrating the feasibility of air strikes on Birkenau. The 15th was doing this with its all-out effort to destroy the cluster of at least eight Nazi synthetic fuel plants in Poland near Upper Silesian coal mines. Buna was one of them.

McCloy told me he was unaware of the 15th's effort but added that at the time, he "must have known" or "probably heard of" it. This would seem to confirm Wyman's belief, set out in a May 1978 Commentary article, that "the possibilities were never investigated in Washington."

The 15th reached its full authorized strength by May 1944, weeks after the Luftwaffe had become a defeated force. On May 8, Wyman wrote, Lt. Gen. Ira C. Eaker, chief of Allied air forces in Italy, assured Air Force leaders that his heavy bombers could make daylight raids on Blechhammer, an oil plant 47 miles from Auschwitz, and that others at Auschwitz and Odertal "might also be attacked simultaneously."

In late June, the 15th began to bomb Buna and other plants as few as 13 miles from Auschwitz. In all, the 15th's B17s and B24s flew more than 2,280 sorties to attack targets close to Birkenau, dropping up to 10 times that many bombs. Contrary to the claims Hull and McCloy were making in November, P51 Mustangs and late-model P38 fighters had been escorting the heavy bombers regularly since May.

The Foggia bases not only didn't require overflights of Germany, but they were about 25 percent closer by air than Britain was to the cluster of German oil plants. Buna, 750 miles from London, was only 600 miles from Foggia. Where the "2,000 mile round trip" figure originated, McCloy says, he doesn't know.

Years later, Birkenau was noticed to be "in perfect alignment" with Buna by Dino A. Brugioni, a retired CIA senior official and expert on aerial reconnaissance and photo interpretation. Brugioni says an aircraft flying to or returning from Buna had to fly directly over the death factory. McCloy says that "I didn't know" either of the alignment or of the closeness of Birkenau to Buna.

In four raids on Buna between Aug. 20 and Dec. 26, 1944, the 15th dropped 3,394 high- explosive, 500-pound bombs. The first attack was by 127 B17s strongly protected by 100 Mustangs. Antiaircraft guns protecting Buna and Birkenau and 19 defending German fighter planes "were ineffective," Wyman wrote. "Only one American bomber went down; no Mustangs were hit." The second strike, by 96 B24 Liberators Sept. 13, met no Nazi fighters, but heavy flak from guns emplaced during the preceding three weeks shot down three bombers.

At this stage, destruction of the death installations would have all but guaranteed that they would not be rebuilt, in Wyman's view, because the Nazis would have had "to commit new and virtually nonexistent manpower resources to mass killing." He said they preferred gas chambers because they were "far more efficient" than gunfire -- they killed 2,000 people in less than half an hour and "required only a limited number of SS men. Killing tens of thousands by gunfire would have required a military force."

Starting April 4, 1944, photo reconnaisance planes based near Foggia flew more than 30 missions over Buna, always photographing Birkenau in the process. In a 1979 CIA monograph, Brugioni and Robert C. Poirier labeled "Extermination operations in progress" on Aug. 25; they had dug out the Air Force photos of Birkenau in an exhaustive year- long search on their own time.

If photo interpreters had been alerted, Brugioni says in the current Military Intelligence, they "would have quickly located" the four gas chamber-crematoria buildings. McCloy says he had never inquired if there were aerial photos of Birkenau. There is no evidence to show that the 15th Air Force discovered or was told that Birkenau was a death factory.

McCloy says his involvement in the Auschwitz question began with a summons from Harry Hopkins, a top aide to FDR who died in 1946, to meet with him and possibly with the late Samuel Rosenman, regarded by some as the "special adviser to Roosevelt on Jewish affairs."

McCloy recalls Hopkins telling him that Jewish spokesmen had told FDR personally that they wanted bombings, but that "the Boss (Roosevelt) was not disposed to" bombing. Hopkins asked him "to inquire of the Air Force as to what the logistics were." McCloy said he already had Arnold's negative appraisal and gave it to Rosenman, and "that was the end of that."

But Wyman says: "I've been unable to find, in years of trying, any documentary evidence that the bombing question ever came to Roosevelt. FDR didn't care enough about the whole issue of rescue to let that issue or any aspect of it become a deep concern; would meet only once with Jewish groups to discuss it, and shunted their written appeals to the State Department."

Wyman doubts that Hopkins p oil pllayed any part in decision-making on the Birkenau bombing, because in the spring and summer of 1944 he was all but incapacitated by cancer and spending a lot of time in treatment and in convalescence. Rosenman would have been aware of any bombing requests reaching the White House, but his biography says nothing about Birkenau, Wyman adds.

Another wartime episode also raises questions about the importance McCloy placed on saving civilian victims of the Nazis.

As one of the three Cabinet members on the War Refugee Board, Secretary of War Henry L. Stimson delegated his authority to McCloy. In a Jan. 28, 1944 letter, the most active member, Treasury Secretary Henry Morgenthau Jr., asked McCloy to send to military theater commanders FDR's directive to the WRB to do all that it could to rescue Nazi victims "who are in imminent danger of death . . . consistent with the successful prosecution of the war."

"I don't remember it (the letter) at all," McCloy says. But the record shows he sent it to the general staff with a notation that, at least in spirit, ran counter to the president's directive. "I am very chary of getting the Army involved in this while the war is on," he wrote.

The general staff then quietly put in place a firm policy of denying use of the armed forces for rescues of the victims of enemy oppresion "unless such rescues are the direct result of military operations conducted with the objective of defeating the armed forces of the enemy."

In February, the War Department followed up with a complementary position: "We must constantly bear in mind the most effective relief which can be given victims of enemy persecution is to insure the speedy defeat of the Axis."

On June 23, Morgenthau sent McCloy a confidential cable from Jewish sources in Europe pleading for bombardment of the rail hubs necessary to the Nazis in deporting 10,000 to 15,000 Jews a day from Hungary and Slovokia to their deaths in Poland. The "suggested reply" of assistant chief of staff Thomas T. Handy argued against "diversion" of resources and for "early defeat of the Axis" as the better answer.

Before the suggested reply reached McCloy, however, it hit a snag: a new plea to save vast numbers of prospective victims with bombings of rail facilities, including some used to carry "many thousand" enemy soldiers a day. The plea was made by Roswell McClelland, the WRB representative in Bern.

Pehle sent McClelland's cable to McCloy, who passed it to his aide, Col. Harrison A. Gerhardt. In a July 3 memo that has added no luster to McCloy's role, Gerhardt told his boss: "I know you told me to 'kill' this (the bombing request relayed by Morgenthau) but since those instructions, we have received the attached letter from Mr. Pehle. I suggest that the attached reply be sent."

That reply, essentially adopted by McCloy the next day, said rail bombings would be of "very doubtful efficacy." Wyman wrote that heavy and sustained bombing "could be very effective," but recognized that "in the midst of war, no one proposed or expected diversion of that kind of military force for rescue purposes."

McCloy once cited an additional objection to rail bombings: "Even if practicable, (they) might provoke even more vindictive action by the Germans."

"What 'more vindictive action' was possible remained the secret of the War Department," Henry L. Feingold wrote in "The Politics of Rescue." McCloy termed Feingold's statement "sort of silly," mainly because bombing could have provoked the Nazis to speed up the murders of their prisoners.

Some doubt that a speedup was possible. In May 1944, for example, the round-the- clock killings at Birkenau, by gassing and gunfire, were peaking at 12,000 or more a day, overtaxing the 46 crematoria furnaces. Excess bodies were being buried in trenches and burned in large open pits.

McCloy was shown a May 31, 1944, aerial photo with a one-word caption, "smoke," put on it in 1979. The caption marked an open pit where bodies overflowing the crl plematoria were being burned.

Looking at the photo, McCloy no longer used the word "silly" to describe Feingold's question. He said that he had gotten the idea of more harassment of prisoners from others, and "I was passing on the concept."

It was not a concept embraced by those with the most at stake: Many prisoners at Auschwitz were found later to have wanted the bombings.