Sixty years after Hiroshima, we now have the secret intercepts that shaped his decision

by Richard B. Frank

The sixtieth anniversary of Hiroshima seems to be shaping up as a subdued affair--though not for any lack of significance. A survey of news editors in 1999 ranked the dropping of the atomic bomb on August 6, 1945, first among the top one hundred stories of the twentieth century. And any thoughtful list of controversies in American history would place it near the top again. It was not always so. In 1945, an overwhelming majority of Americans regarded as a matter of course that the United States had used atomic bombs to end the Pacific war. They further believed that those bombs had actually ended the war and saved countless lives. This set of beliefs is now sometimes labeled by academic historians the "traditionalist" view. One unkindly dubbed it the "patriotic orthodoxy."

But in the 1960s, what were previously modest and scattered challenges of the decision to use the bombs began to crystallize into a rival canon. The challengers were branded "revisionists," but this is inapt. Any historian who gains possession of significant new evidence has a duty to revise his appreciation of the relevant events. These challengers are better termed critics.

The critics share three fundamental premises. The first is that Japan's situation in 1945 was catastrophically hopeless. The second is that Japan's leaders recognized that fact and were seeking to surrender in the summer of 1945. The third is that thanks to decoded Japanese diplomatic messages, American leaders knew that Japan was about to surrender when they unleashed needless nuclear devastation. The critics divide over what prompted the decision to drop the bombs in spite of the impending surrender, with the most provocative arguments focusing on Washington's desire to intimidate the Kremlin. Among an important stratum of American society--and still more perhaps abroad--the critics' interpretation displaced the traditionalist view.

These rival narratives clashed in a major battle over the exhibition of the Enola Gay, the airplane from which the bomb was dropped on Hiroshima, at the Smithsonian Institution in 1995. That confrontation froze many people's understanding of the competing views. Since then, however, a sheaf of new archival discoveries and publications has expanded our understanding of the events of August 1945. This new evidence requires serious revision of the terms of the debate. What is perhaps the most interesting feature of the new findings is that they make a case President Harry S. Truman deliberately chose not to make publicly in defense of his decision to use the bomb.

When scholars began to examine the archival records in the 1960s, some intuited quite correctly that the accounts of their decision-making that Truman and members of his administration had offered in 1945 were at least incomplete. And if Truman had refused to disclose fully his thinking, these scholars reasoned, it must be because the real basis for his choices would undermine or even delegitimize his decisions. It scarcely seemed plausible to such critics--or to almost anyone else--that there could be any legitimate reason that the U.S. government would have concealed at the time, and would continue to conceal, powerful evidence that supported and explained the president's decisions.

But beginning in the 1970s, we have acquired an array of new evidence from Japan and the United States. By far the most important single body of this new evidence consists of secret radio intelligence material, and what it highlights is the painful dilemma faced by Truman and his administration. In explaining their decisions to the public, they deliberately forfeited their best evidence. They did so because under the stringent security restrictions guarding radio intercepts, recipients of this intelligence up to and including the president were barred from retaining copies of briefing documents, from making any public reference to them whatsoever at the time or in their memoirs, and from retaining any record of what they had seen or what they had concluded from it. With a handful of exceptions, they obeyed these rules, both during the war and thereafter.

Collectively, the missing information is known as The Ultra Secret of World War II (after the title of a breakthrough book by Frederick William Winterbotham published in 1974). Ultra was the name given to what became a vast and enormously efficient Allied radio intelligence organization, which secretly unveiled masses of information for senior policymakers. Careful listening posts snatched copies of millions of cryptograms from the air. Code breakers then extracted the true text. The extent of the effort is staggering. By the summer of 1945, Allied radio intelligence was breaking into a million messages a month from the Japanese Imperial Army alone, and many thousands from the Imperial Navy and Japanese diplomats.

All of this effort and expertise would be squandered if the raw intercepts were not properly translated and analyzed and their disclosures distributed to those who needed to know. This is where Pearl Harbor played a role. In the aftermath of that disastrous surprise attack, Secretary of War Henry Stimson recognized that the fruits of radio intelligence were not being properly exploited. He set Alfred McCormack, a top-drawer lawyer with experience in handling complex cases, to the task of formulating a way to manage the distribution of information from Ultra. The system McCormack devised called for funneling all radio intelligence to a handful of extremely bright individuals who would evaluate the flood of messages, correlate them with all other sources, and then write daily summaries for policymakers.

By mid-1942, McCormack's scheme had evolved into a daily ritual that continued to the end of the war--and is in essence the system still in effect today. Every day, analysts prepared three mimeographed newsletters. Official couriers toting locked pouches delivered one copy of each summary to a tiny list of authorized recipients around the Washington area. (They also retrieved the previous day's distribution, which was then destroyed except for a file copy.) Two copies of each summary went to the White House, for the president and his chief of staff. Other copies went to a very select group of officers and civilian officials in the War and Navy Departments, the British Staff Mission, and the State Department. What is almost as interesting is the list of those not entitled to these top-level summaries: the vice president, any cabinet official outside the select few in the War, Navy, and State Departments, anyone in the Office of Strategic Services or the Federal Bureau of Investigation, or anyone in the Manhattan Project building the atomic bomb, from Major General Leslie Groves on down.

The three daily summaries were called the "Magic" Diplomatic Summary, the "Magic" Far East Summary, and the European Summary. ("Magic" was a code word coined by the U.S. Army's chief signal officer, who called his code breakers "magicians" and their product "Magic." The term "Ultra" came from the British and has generally prevailed as the preferred term among historians, but in 1945 "Magic" remained the American designation for radio intelligence, particularly that concerning the Japanese.) The "Magic" Diplomatic Summary covered intercepts from foreign diplomats all over the world. The "Magic" Far East Summary presented information on Japan's military, naval, and air situation. The European Summary paralleled the Far East summary in coverage and need not detain us. Each summary read like a newsmagazine. There were headlines and brief articles usually containing extended quotations from intercepts and commentary. The commentary was critical: Since no recipient retained any back issues, it was up to the editors to explain how each day's developments fitted into the broader picture.