Little Boy

Little Boy was the name given to an atomic bomb whose U-235 portion was delivered to Tinian on July 26, 1945. Its appearance in the account marks a turning point: a project that had reached Harry S. Truman first as a guarded secret became an imminent weapon, and the bomb’s use at Hiroshima brought that secret into the war’s visible, irreversible consequences.

A secret project becomes a presidential concern

By June 1943, investigators working with Truman’s Senate committee had encountered unexplained expenditures for a vast undertaking identified only as the Manhattan Project, larger even than the Canol Project. When Truman asked Secretary of War Stimson about it, Stimson said that only a handful of people knew the secret development. Truman accepted his assurance that it served a specific and unique purpose and did not press him for details.

Information nevertheless reached Truman by other means. By July he understood the essential nature of the project, and he used that knowledge in a letter to Lewis Schwellenbach, who had asked about immense land condemnations for DuPont along the Columbia River near Hanford. The seizure involved nearly half a million acres. Truman reassured Schwellenbach, while the public explanation remained circumscribed; the scale of the land acquisition offered a measure of the project’s reach without disclosing its purpose.

The weapon’s scale and the choices around it

In a later briefing, Stimson brought Truman a memorandum warning that within four months the United States would probably have completed a weapon capable of destroying an entire city. Stimson also stressed that the United States alone then had the capacity to produce it, though he expected that monopoly to be temporary and believed the Soviet Union might become a producer within a few years. The bomb therefore entered Truman’s deliberations not only as a means of ending the war, but as a development with consequences for the postwar balance of power.

The weapon’s potential was not yet the explicit subject of every planning discussion. As Truman weighed invasion against bombing and blockade, he called the choice of Japanese strategy his hardest decision to date; his diary entry did not mention the secret project. At a White House meeting on June 18, the invasion plan proceeded as though the bomb did not exist. The proposed first phase, an assault on Kyushu, was expected to begin in November, and General George C. Marshall estimated approximately 31,000 losses in its first thirty days by comparison with Luzon. The contrast between that projection and Stimson’s warning gave the still-secret weapon a place in decisions whose human costs were already being assessed.

A report on the earlier atomic test conveyed the force involved in concrete terms. Half a mile from the explosion stood a 220-ton steel test cylinder, set in concrete and surrounded by a heavily braced, 70-foot steel tower. The blast tore the tower from its foundations, twisted it apart, and flattened it, although those observing the test had not expected it to be damaged. This was not a description of Little Boy itself, but it made the destructive capacity of the developing weapon difficult to treat as an abstraction.

Delivery and the terms of surrender

On July 26, the cruiser USS Indianapolis delivered the U-235 portion of an atomic bomb, nicknamed Little Boy, to Tinian. That evening, Truman and James F. Byrnes decided to issue the Potsdam Declaration with Clement Attlee and Chiang Kai-shek. The declaration promised humane treatment and said the Japanese people would not be enslaved or destroyed as a nation; it described a postwar Japan with its warmaking power removed, freedoms established, and a peacefully inclined government freely elected.

The wording made a careful distinction between Japan as a nation and its armed forces. Unconditional surrender was demanded of the armed forces, not explicitly of the Japanese nation, while the alternative was described as prompt and utter destruction. The declaration did not name Emperor Hirohito or explain what that destruction would entail. In the sequence of the account, the weapon’s arrival and the ultimatum thus stand close together: the warning’s force depended partly on a power whose precise form remained undisclosed.

Hiroshima and the secret made visible

On August 6, Truman was at sea aboard the presidential ship when he received a decoded message from the Secretary of War. He was below deck, having lunch with six enlisted men, and Captain Graham handed him a map of Japan with Hiroshima circled in red. The message reported that the city had been bombed four hours earlier and that the results were successful, with visible effects greater than in any test.

Truman reacted with excitement, took Graham’s hand, and sent him to show the message to Byrnes. A second report followed minutes later, describing the bombing as a complete success. The scene joined the vast machinery of the secret project to a small, specific object—a map marked in red—and to a message delivered in the middle of an ordinary meal. Little Boy’s significance lies in that passage from guarded knowledge to action: what had once been concealed behind unexplained expenditures and assurances now registered as the destruction of a named city, and as a decision whose consequences reached beyond the end of the war.