Summer of Decision

Summer of Decision names the pivotal summer of 1945 in Harry S. Truman’s presidency, when the war against Japan, the prospect of invasion, and the newly developed atomic bomb converged in decisions of extraordinary consequence. The period is not presented as a single moment of revelation: its pressures accumulated through Truman’s Senate oversight, the difficult transition after Franklin D. Roosevelt’s death, and deliberations in which advisers disagreed about risks and means. Its defining tension is between the urgency to end the war and the uncertainty surrounding what each available course would cost.

A Decision-Maker Before the Decision

Before Truman faced the atomic question as president, his Senate investigations had begun uncovering a secret enterprise larger than the Canol Project. Staff investigators encountered puzzling expenditures connected to the Manhattan Project. On June 17, 1943, Truman telephoned Henry L. Stimson, then Secretary of War. When Stimson described the matter as a highly important secret development and assured him it had a specific, unique purpose, Truman accepted that assurance and did not press him for further details. By July, he had learned enough about the project’s essential nature to reassure Lewis Schwellenbach, who was concerned about enormous land condemnations along the Columbia River near Hanford, involving nearly half a million acres.

The investigations raised Truman’s standing in the Senate. Even liberals who had once regarded him as conscientious but unremarkable came to respect his willingness to challenge powerful military and industrial interests. Claude Pepper recalled that Truman had dared to demand evidence and had caught influential figures in wrongdoing. That oversight experience mattered to the summer of 1945, but it did not make the new president fully informed: the atomic project had remained closely guarded, and the responsibility for what to do with the weapon would ultimately be his.

The transition into the presidency brought an immediate test of both continuity and independence. At a landmark White House meeting on April 23, Truman sat with officials who had served Roosevelt, including Edward R. Stettinius Jr., Stimson, James Forrestal, George C. Marshall, Ernest J. King, William D. Leahy, W. Averell Harriman, and Charles Bohlen. No one from Truman’s former Senate staff or his Missouri circle was present. The discussion turned to Poland, where the Soviet Union was insisting on a government unacceptable to the United States. Though Truman had recently assured Vyacheslav Molotov that he would honor commitments made by Roosevelt, he now complained that dealings with the Soviets seemed one-sided and warned that they could not expect American cooperation without offering their own.

The Bomb Becomes a Presidential Burden

Stimson made the weapon’s scale unmistakable in a private meeting with Truman. Alone in the President’s office, he handed over a several-page memorandum whose opening warned that within four months the United States would probably have completed the most terrible weapon in human history, capable of destroying a city with one bomb. The United States and Britain had shared in its development, but only the United States then had the capacity to produce it. Stimson also warned that this advantage could not last indefinitely and that the Soviet Union might be able to join the nuclear powers within a few years.

The Interim Committee on S-1, an entirely civilian and highly secret advisory body chaired by Stimson, brought government officials and scientists into the deliberation. Its membership included James Bryant Conant, Karl Compton, Vannevar Bush, Ralph A. Bard, William L. Clayton, George L. Harrison, and James F. Byrnes. At its first meeting, on May 9, 1945, Stimson told the group that its recommendations might turn the course of civilization. On May 31, the committee met for two days with an advisory panel of physicists, including J. Robert Oppenheimer, head of the Los Alamos Laboratory. The panel and committee considered a technical demonstration away from a city, but the proposal was rejected because they judged that no demonstration would provide the decisive shock they sought.

Stimson stressed that the committee advised; it did not make the decision for the President. He regarded the recommendation as his own responsibility and believed that a dramatic demonstration of American power could compel Japan’s leadership to surrender, thereby saving more American and Japanese lives than it would cost. The reasoning joined a military objective to a stark moral calculation. It also placed a limit on what committee deliberations could settle: the ultimate responsibility remained with the President.

That responsibility was not always visible in the operational planning. On June 18, Truman considered whether to invade Japan or instead bomb and blockade it, calling it the hardest decision he had faced to that date. Yet the atomic project was not discussed at the White House meeting that reviewed invasion plans, a silence that struck John J. McCloy as though the bomb did not exist. Marshall proposed a two-phase invasion beginning in November with Kyushu, only 350 miles from Okinawa. He compared the operation’s difficulty to Normandy and estimated about 31,000 losses during its first 30 days, using the losses on Luzon as a point of comparison. Truman’s stated priority was to minimize American deaths; time and money were secondary. At this stage, his diary framed the immediate choice as invasion versus bombing and blockade, without mentioning S-1.

Potsdam and the Point of Commitment

The summer’s decisions unfolded alongside the diplomacy at Potsdam. Truman arrived reluctant to make the journey and wrote of the preparations required for meeting Stalin and Winston Churchill. By the second week, he knew that decisions about the bomb could no longer be deferred. On July 22, he attended both a Protestant service and a Catholic mass led by Father Curtis Tiernan, an old friend from Battery D whom he had asked to come to Berlin. In writing to Bess Truman, he connected the coming week’s demands with his need for divine help.

On the morning of July 24, Stimson again went to Truman’s office with a message. The decisive conversation was not recorded on paper, but the account places the critical moment later that morning, at 11:30, in the dining room at Number 2 Kaiserstrasse. Truman, Churchill, and their military advisers were gathered around the table. From that point, the plan was settled: barring an unforeseen development, the bomb would be used within weeks. Truman later identified that same day as the day he informed Joseph Stalin.

The disclosure came after a contentious session at Cecilienhof Palace. As the meeting broke up, Truman walked across the room to Stalin and casually mentioned that the United States had a new weapon of unusual destructive force. Stalin replied that he was glad to hear it and hoped it would be used against Japan. The contrast between the bomb’s immense importance and the casual form of the announcement marks the moment: the decision had been made, but Truman revealed only limited information about the weapon. In his later account, he insisted that the final choice of where and when to use it belonged to him, and that he viewed the bomb as a military weapon recommended for use by his senior military advisers.

The Wider Pattern of Decision

The title’s summer is a concentrated episode in a longer chronology of presidential choices under pressure, not the only such test in the book. In 1946, during the railway strike crisis, Truman privately drafted a seven-page speech on a small ruled tablet. He had no intention of delivering it; writing it was a way to release anger amid pressure from the strike, injured men, and what he felt was disloyalty from former allies. The episode shows a different side of decision-making: an unissued draft rather than a public order, and an intense private reaction rather than a settled policy.

In 1947, the approaching British withdrawal from Greece turned an anticipated problem into an immediate demand for action. After Dean Acheson and others prepared a report over the weekend, George C. Marshall and Acheson urged swift aid to Greece and, to a lesser extent, Turkey. Truman agreed that substantial help for Greece was needed quickly; the amount required for the remainder of 1947 was a quarter of a billion dollars. The question had widened beyond an aid bill into a larger response to the crisis, linking practical assistance with the direction of American policy.

The same burden of choosing amid competing risks reappeared in the hydrogen-bomb debate. At the final session of the Z Committee on January 31, 1950, Dean Acheson presented a proposed presidential statement supporting work on the weapon. Louis A. Johnson agreed, while David E. Lilienthal warned that proceeding could foreclose a different approach to the arms race, distort defense priorities, and give the public a dangerous sense of security. Acheson concluded that delay would not stop Soviet development and that Americans would not accept a policy of waiting. These later disputes do not belong to the summer of 1945 itself; they show how the summer’s central problem—how to choose when the alternatives all carry grave consequences—continued to recur.

The Korean crisis offered another compressed test. On June 25, 1950, Truman returned from Missouri to Washington, where Dean Acheson, Louis A. Johnson, and James Webb were waiting at National Airport. Before landing, Truman had asked for an emergency meeting at Blair House. During the flight, he thought about earlier failures to resist aggression and the consequences of allowing North Korea to force its way into the Republic of Korea. The attack had been a surprise despite incidents along the 38th parallel: American troops had recently left South Korea, and Dean Acheson had not included Korea in his January account of American interests in the Pacific. The episode underscores the conditions that give Summer of Decision its meaning: urgent choices, incomplete foresight, and the knowledge that a decision not to act also carries consequences.