The brouhaha over the Air and Space Museum's planned exhibition next year of the Enola Gay is but a foretaste of what we can expect on the 50th anniversary of the end of the Pacific phase of World War II after the United States dropped atomic bombs over Hiroshima and Nagasaki. And I think it's damned important, in part because I was involved.

My nickel's worth had to do with the estimates of potential casualties should the United States have to invade Japan to end the war. I was a civilian in uniform, following movements of Japanese kamikaze units by use of intercepted and decoded enemy military messages. That led to estimating what Japanese planes might be available to attack American troops wading ashore on Kyushu, the westernmost main island, on Nov. 1, the date set for what was code-named Operation Olympic. Casualty estimates derived from our view of Japanese capabilities to resist such an invasion.

I've been through a mass of now declassified data in the National Archives having to do with these casualty estimates. And I've read a lot of what the revisionists contend: that such estimates were wildly inflated and, anyway, the real issue is the immorality of the Bomb and the racism they see implicit in dropping it on the Japanese. (We can never know, though I feel certain, that it would have been used on Hitler and his Nazis had it been ready in time.)

Context is vital in judging history of half a century ago, and my generation can never forget the ferocity of Japanese defenders of their captured empire from Guadalcanal through the Philippines to the Marianas and, especially, the defense of the Japanese island of Okinawa.

Indeed, the costly battle for Okinawa was very much on everybody's mind, from Harry Truman, the new president, down to me, a second lieutenant in the Army Air Corps working in a windowless room in the Pentagon. Why? Because the kamikazes, the so-called suicide, attacks on our ships had extracted a terrible toll.

The best figures I've seen tell us that kamikaze attacks sank 30 vessels and damaged 368 including 10 battleships and 13 aircraft carriers, the heaviest toll in naval history. More than 12,000 Americans died to take that island, 36,000 more were wounded while the Japanese had 110,000 military deaths and perhaps 150,000 civilians dead, many of whom committed suicide rather than surrender.

The Kyushu invasion date was set by the Joint Chiefs on May 25, 1945, just after the German surrender in Europe and some six weeks after President Franklin Roosevelt's death. That casualties had long been on the leaders' minds is vividly demonstrated by a fragment from journalist Joseph C. Harsch's recent autobiography. He tells of walking into the White House office of Adm. William D. Leahy, then FDR's chief of staff, around the first of February 1945, to be greeted with: "Harsch, how do you think the American people would react to half a million casualties on the beaches of Japan?"

That was well before Okinawa. More precise casualty estimates were worked up for a White House meeting, called by Truman, on June 18 as the Okinawa struggle was ending. It was at this meeting that Truman was quoted, in the minutes, this way: "He had hoped that there was a possibility of preventing an Okinawa, from one end of Japan to the other." And after discussing the proposed landings on Kyushu, Truman "expressed the view that it was practically creating another Okinawa closer to {the heart of} Japan, to which the Chiefs of Staff agreed."

Adm. Leahy reported that in capturing Okinawa our troops "had lost 35 percent in casualties." The assault force planned for Kyushu numbered 766,700 and 35 percent of that -- which Leahy said "would give a good estimate of the casualties to be expected" -- would have come to more than 268,000. Gen. George C. Marshall, the army chief, generalized the casualty figure in defeating Japan after landings in both Kyushu and the main island of Honshu at from half a million to a million. Secretary of War Henry L. Stimson used those figures. After the war and after he left the White House, Truman talked of a possible 250,000 dead and half a million wounded, his justification for using the Bomb to end the war without invasion.

At war's end, Marshall's report to the public stated: "Defending the homeland the enemy had an army of 2 million, a remaining air strength of 8,000 planes of all types, training and combat." Most of those planes probably would have been used, if we had not by then destroyed them, as kamikazes.

From the Potsdam Conference in Berlin on July 18, 1945, Truman wrote to his wife, Bess, that Joseph Stalin had then agreed to enter the war on Aug. 15. To this Truman added: "I'll say that we'll end the war a year sooner now, and think of the kids who won't be killed!" This evidence does not fit the revisionist thesis that the United States used the Bomb, in part at least, to intimidate the Soviet Union. It was used to prevent casualties.

Here I've picked out only some bits of a mass of evidence now on the record to show how fearful the American leadership, both civilian and military, was of huge casualties that would be suffered if Japan were to be invaded. Estimates surely were wobbly, but I think they were at least in the ballpark. That opinion derives, in part, from my inspection of Kyushu and its mountainous terrain and shallow beaches shortly after the surrender, plus my and others' interrogation of Japanese military personnel. We were part of the U.S. Strategic Bomb Survey.

The Enola Gay dropped the Bomb on Aug. 6, and the Soviets, scenting war's quick end, came in two days later, not waiting for their promised date of Aug. 15. They wanted a piece of Japan's empire and a say in Japan's future.

The Air and Space Museum's exhibit planned for next year's 50th anniversary has a lot to encompass, not the least of which is to be true to the context of history.

The writer covered local, national and international news for The Post for 23 years.