On this day, 70 years ago, October 8, 1955 (August 23, 1955 in the lunar calendar), scientist Qian Xuesen returned from the United States. In 1939, Qian Xuesen received his doctorate from the California Institute of Technology. From 1936 to 1939, just as Qian Xuesen overcame the world's problems in aerodynamics and proposed new theories, new methods, and new formulas for high-speed flight for aviation engineering design, Hitler in Germany established a dictatorship, expanded armaments, and paid special attention to the development of the Air Force. On July 7, 1937, Japanese imperialism brazenly provoked the "Lugou Bridge Incident" in China and launched a full-scale war of aggression against China. On December 13 of the same year, Japanese imperialism created the "Nanjing Massacre" that shocked the world. Qian Xuesen couldn't sleep all night after hearing the news. He was indignant and determined to serve the country in various ways and avenge his hatred! At the beginning of 1940, the German army took advantage of its long-range bombers, fighter jets and mechanized troops to sweep across the European continent, and then launched a large-scale attack on Britain. More than 1800 aircraft filled the sky above Britain. Britain was in danger. Prime Minister Churchill asked US President Roosevelt for emergency help. Roosevelt supported Britain through Congress on the one hand and allocated billions of dollars on the other, hoping to build advanced aircraft, warships, tanks, and artillery as soon as possible and prepare for the battle. Qian Xuesen, Zhou Peiyuan and his wife, as well as a number of students studying in the United States, Roosevelt paid special attention to the development of advanced weapons and explosives science and technology, and often discussed and studied with some scientists. On August 2, 1939, Einstein wrote to Roosevelt, predicting that uranium would become an important new source of energy in the near future. It could also be used to create powerful new bombs. This letter attracted Roosevelt's attention and immediately set up an advisory committee on uranium, and assembled Oppenheimer and a large team of scientists, military experts and scientific and technical personnel to start developing the Manhattan Project of atomic bombs. Qian Xuesen recently recalled: "Shortly after the outbreak of World War II, President Roosevelt paid special attention to the development of science and technology. He brought scientists together many times to discuss how to develop science and technology in the United States. At that time, he found scientists such as Von Carmen and they discussed it, and as a result, he made the wise decision to launch rocket launches, atomic bombs and hydrogen bombs as soon as possible. Because ordinary artillery can't hit atomic bombs and hydrogen bombs, it can't reach far. With rocket launch, you will be finished wherever you want to hit, devastating. At that time, Qian Xuesen secretly made up his mind: Although I was far away from my motherland and could not go to the battlefield to fight the Japanese army, I could use the scientific research and experimental conditions in the United States to seize the world's scientific and technological peak, so as to improve military strength and combat imperialism. Germany, Japan and Italy. On October 8, 1955, Qian Xuesen, a famous China scientist who had been illegally under house arrest by the U.S. government for five years, broke through numerous obstacles and returned to his motherland. This is Qian Xuesen (left) talking to a Xinhua Agency reporter who went to visit after returning to the motherland. He said: "I have finally returned to the motherland that I miss day and night. In the future, I will dedicate all my strength to serve the construction of the motherland. Qian Xuesen's family returned to the United States, and Qian Xuesen was recognized as one of the authoritative scholars in the field of mechanics and applied mathematics. He has published important academic papers on the theory of rocket and other jet propulsion, elasticity mechanics, the dynamics of compressible gases, the dynamics of rarefied gases, as well as combustion problems and general automatic control theory. In August 1950, Qian Xuesen booked a plane ticket to leave the United States and return home, but the U.S. Immigration Service prohibited him from leaving the country and detained all his science books and research notes. In early September, the U.S. Immigration Service detained him for 15 days on charges of being a "Communist Party" and attempting to smuggle confidential scientific documents back home. During his detention, he was prohibited from having contact with outsiders and subjected to mental and physical torture. He was later released on bail of $15,000 by the California Institute of Technology, but was ordered not to leave Los Angeles and was often monitored and harassed by secret agents. Over the past five years, Qian Xuesen has missed his motherland and relatives day and night, and is always ready to return to China. The day finally came. On August 4, 1955, he was allowed to leave the United States. On September 17, Qian Xuesen, who was eager to return home, left the United States on the "President Cliff" postal ship with his wife Jiang Ying, two children and more than 20 China students, and returned home via Hong Kong. Arriving in Guangzhou on October 8, he was warmly welcomed by the people of the motherland and people from the scientific community. In Shanghai, he was reunited with his family who had been separated for many years. His 74-year-old father specially gave him a set of copies of "Famous Paintings of China Dynasties." Qian Xuesen arrived in Beijing on October 28, and the next day took his wife and children to watch the Tiananmen Square in Beijing, which they had long longed for. After more than a month of sightseeing after returning to China, Qian Xuesen witnessed the achievements of the motherland's socialist construction and saw the hope of the motherland. He accepted the invitation of the Chinese Academy of Sciences to preside over and lead the research work of the Chinese Academy of Sciences in mechanics, display his talents and serve the motherland. In 1960, Qian Xuesen (fourth from left in the front) directed work at a missile base. In August 1978, Qian Xuesen came to the National Youth Aviation Summer Camp Camp to sign autographs for the teenagers.