Today in History: Detonation of 10.4-Megaton Ivy Mike Hydrogen Bomb

M.C. Millman

In January of 1950, President Truman made his controversial announcement regarding the continued research and production of thermonuclear weapons, also referred to as hydrogen bombs.

Amid growing Cold War tensions, the United States did not want to be overtaken in a nuclear arms race by the Soviet Union.

"It is part of my responsibility as Commander in Chief of the Armed Forces to see to it that our country is able to defend itself against any possible aggressor," declared Truman. "Accordingly, I have directed the AEC to continue its work on all forms of atomic weapons, including the so-called hydrogen or Super bomb."

Truman's announcement came to fruition less than three years later. A series of two tests were planned, known as Operation Ivy. The first test occurred on November 1, 1952, at 07:15 a.m.. The 10.4-megaton Ivy Mike hydrogen bomb was detonated on Elugelab Island in the South Pacific Marshall Islands. 

According to the Radiochemistry Society, the device weighed 82 tons. It was the fourth-largest device ever tested by the United States. The Island that Ivy Mike was detonated on was entirely destroyed, with the bomb leaving a massive crater 6,240 ft in diameter and 164 ft deep.

The Atomic Heritage Foundation wrote that Ivy Mike's explosion yielded an energy equivalent of ten megatons of TNT, which was almost one thousand times as large as that released by the Hiroshima bomb dropped on Japan in 1945. 

The second device tested under Operation Ivy,  known as the King Shot,  was detonated on November 16, 1952. This was followed by Operation Castle, which took place in the spring of 1954 with the testing of six different superbombs.  

"The world suddenly shifted from the path it had been on to a more dangerous one. Fission bombs, destructive as they might have been, were thought of [as] being limited in power," said Physicist Herbert York regarding the implications of the first thermonuclear device, according to PBS. "Now, it seemed we had learned how to brush even these limits aside and to build bombs whose power was boundless."