Seventy-two years ago today, on January 7, 1953 (November 22, 1952), Truman announced that the United States had developed a hydrogen bomb. The MK17 hydrogen bomb, the first air-dropped hydrogen bomb developed by the United States in the 1950s, weighed 21 tons and was almost the size of a small locomotive. The Soviet Union's successful atomic bomb test in September 1949 shocked the United States, and it was necessary to build a more powerful bomb for strategic reasons. In January 1950, US President Truman decided to develop a hydrogen bomb. The research on the hydrogen bomb was led by Hungarian scientist Taylor, who used the atomic bomb to promote the high temperature generated by the explosion to cause deuterium to fuse. In May 1951, the preparations for the principle test of the hydrogen bomb were in order. The test bomb was code-named "George" and was carried out at the Enniwittok Island test site in the Pacific Ocean. The extremely bulky test device, which reached 62 tons, was placed on a steel frame of more than 60 meters. The device used liquid deuterium as a nuclear fusion charge, and had a cooling system to keep deuterium at extremely low temperatures. The test proved that the explosive power was much higher than that of the atomic bomb. The success of the principle test of the hydrogen bomb greatly advanced the work of making a real hydrogen bomb. On November 1, 1952, another hydrogen bomb test device "Mike" exploded on Enniwittok Island in the Pacific Ocean. The device was 6 meters high, 1.8 meters in diameter, and weighed 65 tons. It looked like a large thermos, and the explosive power was 10 million tons of Tien equivalent. Equivalent to 500 times the size of the Hiroshima-type atomic bomb. The "Mike" is larger than a truck, and it must be equipped with a benzene-heavy refrigeration system. Such a device cannot be carried by aircraft or missiles, and has no actual combat value. Later, people used lithium-6, an isotope of lithium, and lithium deuterium, a compound of deuterium, as nuclear fuel. Lithium deuteride is a solid, does not need to be cooled and compressed, is inexpensive to make, small in size, light in weight, and easy to carry. This kind of hydrogen bomb is called a "dry" hydrogen bomb. In 1954, the first practical hydrogen bomb of the United States was successfully tested on the island of Bifa. In August 1953, the Soviet Union announced that the hydrogen bomb test was successful. Then Britain (May 1957) and France (August 1858) also had hydrogen bombs. China successfully tested the principle of a hydrogen bomb on December 28, 1966, and successfully tested a 3 million-ton hydrogen bomb dropped by an aircraft on September 17, 1967.