Ivy Mike

Ivy Mike was a thermonuclear weapons test whose 10.4-megaton explosion vaporized the Pacific island of Elugelab. In the narrative, it is both the outcome of a policy decision and a stark rebuttal to scientists who had urged restraint: the test they could not publicly oppose went ahead, while its destruction gave visible form to their warnings about the scale and consequences of the Super.

The case against the Super

The objections that preceded the test were strategic as well as moral. In 1949, J. Robert Oppenheimer and the majority of the General Advisory Committee argued that a thermonuclear weapon, if feasible, might yield as much as 100 million tons of TNT, compared with the 15,000-ton yield attributed to the Hiroshima bomb. Such a weapon could destroy hundreds of square miles; the committee warned that it might become a weapon of genocide. Even held in reserve, the Super could damage American interests by making other countries believe the United States was willing to contemplate annihilation.

The committee also challenged the assumption that building the weapon would deter the Soviet Union. If the Soviets pursued a Super, the report argued, an American crash program would not stop them; existing atomic weapons could provide a comparably effective reprisal. The committee instead favored producing fissionable material for smaller tactical weapons and strengthening conventional forces in Western Europe. That alternative carried its own tension: J. Robert Oppenheimer later argued for bringing nuclear weapons onto the battlefield to support military operations, a policy that could make their actual use more likely even as it rejected city-destroying warfare.

Moratorium rejected

By 1952, J. Robert Oppenheimer and his colleagues were pressing for a moratorium on thermonuclear testing and a policy against first use. They knew the first thermonuclear device, code-named Mike, was scheduled for that autumn, and expected the Air Force to oppose any attempt to stop it. Their arguments also rested on a prediction about the test’s effects: a successful demonstration would encourage Soviet efforts, while analysis of radioactive fallout might give Soviet scientists useful evidence about the device.

The panel could not take its concerns to the public without risking their security clearances. On October 9, 1952, the National Security Council rejected the proposed moratorium. The Defense Secretary urged that the idea be put out of mind and any papers about it destroyed, fearing that disclosure would give Joseph McCarthy an opportunity to investigate the State Department and its advisers. The debate thus ended not with an open public decision but with a rejected proposal kept under wraps.

Detonation and its immediate meaning

Three weeks after that rejection, the United States exploded the 10.4-megaton device in the Pacific. The blast vaporized Elugelab. The test was a physical demonstration of the immense destructive capacity that the committee had discussed in estimates and strategic arguments; it also enacted the very demonstration the committee had urged the United States not to make. James B. Conant, one of the scientists who had opposed the crash program, told a Newsweek reporter, “I no longer have any connection with the atomic bomb. I have no sense of accomplishment.”

Aftermath among the scientists

A week later, J. Robert Oppenheimer sat with nine other members of the Science Advisory Committee to the Office of Defense Mobilization as they considered whether to resign in protest. Some scientists took the test as evidence that the government did not intend to heed their expert advice. An old friend of J. Robert Oppenheimer circulated a draft resignation letter, but the group set it aside, holding to the faint hope that the next administration might change course.

That hesitation did not mean the test had reassured them. During the discussion, a warning passed among the advisers that people in the Air Force would pursue J. Robert Oppenheimer and that his colleagues needed to be prepared. The passage from rejected moratorium to detonation and then to a deferred protest marks the test’s larger significance: scientific counsel had been offered, kept secret, and overruled, while the weapon itself supplied a forceful answer to the question of what restraint had been intended to prevent.