Los Alamos Target Committee's principles for selecting targets in Japan

Los Alamos Target Committee's principles for selecting targets in Japan were formed in spring 1945 around the choice of a large urban target, while proposals to warn Japanese civilians received little support. The deliberations placed technical expertise beside military authority but did not give the scientists control over the decision. Their significance grew in retrospect as J. Robert Oppenheimer later condemned the prospect of nuclear genocide, yet also argued for tactical weapons as an alternative to strategic attacks on cities.

The Target Committee's deliberations

Two meetings of General Leslie Groves’s Target Committee took place in Oppenheimer’s office on May 10 and 11, 1945. The official minutes record agreement that the target should be in a large urban area more than three miles in diameter. The participants also discussed the possibility of targeting the emperor’s palace in downtown Tokyo. These recorded principles made the city itself—not merely a discrete military installation—the contemplated scale of attack.

Phil Morrison, a former student of Oppenheimer who had become one of his close friends at Los Alamos, attended as a technical expert. He proposed a formal warning if a demonstration of the bomb seemed impractical, believing that even leaflets could give Japanese civilians an opportunity to evacuate. His intervention brought the human consequences of target selection into a meeting otherwise organized around military planning.

The rejected warning

An Army officer dismissed Morrison’s proposal on the grounds that a warning would expose the attacking aircraft to Japanese defenses. Morrison recalled that he received no support from Oppenheimer. David Hawkins, who was also present, later corroborated the substance of Morrison’s account: Morrison had asked that a warning give civilians a chance to leave, and the officer argued that the Japanese would send everything they had against the planes.

Morrison came away believing that the scientists had little influence over what would happen. His recollection complicates any picture of scientific advisers as a unified force shaping the bomb’s use: at this meeting, a participant could raise the possibility of warning civilians, but the proposal was quickly shut down, and Oppenheimer did not back it. The recorded target standard and the remembered exchange together show how the choice of an urban target proceeded without an adopted civilian warning.

From target selection to the Super debate

Oppenheimer’s later arguments against the hydrogen bomb gave the target question a broader moral and strategic frame. In 1949, as chair of the General Advisory Committee, he joined colleagues who judged that a thermonuclear weapon would be so powerful that any legitimate military target would be too small. A weapon with a possible yield of 100 million tons of TNT, compared with 15,000 tons for the Hiroshima bomb, could destroy 150 to 1,000 square miles or more. The committee warned that the Super might become a weapon of genocide and argued that possessing it could damage American security as well as world opinion.

The committee majority also challenged the assumption that matching a possible Soviet thermonuclear weapon required building one. It argued that the United States’ existing stock of atomic bombs could provide comparably effective reprisals, while a buildup of smaller tactical weapons and conventional forces in Western Europe could offer a more credible defense. On November 9, 1949, the Atomic Energy Commission voted three to two to endorse the committee’s recommendations against a crash program. Oppenheimer thought the immediate contest had been won, but supporters of the hydrogen bomb mounted a counteroffensive.

The unresolved tension in Oppenheimer's strategy

Oppenheimer’s opposition to city-destroying strategy did not lead him to reject every battlefield use of nuclear weapons. In 1951, after seeing an Air Force plan calling for the obliteration of Soviet cities, he was appalled by its scale. Yet he also helped argue in the Project Vista report that tactical atomic weapons could support military forces in a campaign and were not primarily weapons of totality or terror. He hoped to replace plans for strategic annihilation with more limited military objectives, but that alternative carried its own danger: tactical weapons might make nuclear use more likely and serve as a tripwire to a larger exchange.

By 1953, Oppenheimer was describing the American plan as a massive, initial, unremitting strategic assault on the enemy. His arguments about nuclear candor and the dangers of secrecy addressed a later policy debate, not the May 1945 Target Committee meetings. Taken together, however, these episodes trace a persistent problem in his thinking and in American nuclear policy: rejecting the deliberate destruction of cities did not settle how nuclear force could be used without widening the path to catastrophic war.