On this day, 86 years ago, on August 2, 1939 (June 17, 1939 in the lunar calendar), Einstein wrote to Roosevelt, proposing to build an atomic bomb before Germany. On August 2, 1939, out of great concern for the fate of mankind, Einstein, at the request of several other scientists, wrote a letter suggesting that the United States must build an atomic bomb before Germany. A letter drafted by someone else and signed by Einstein read: Mr. President: I have read the manuscripts of Fermi and Szillard's recent research work. This led me to predict that elemental uranium will become a new and important energy source in the near future. Considering this situation, people should be vigilant. If necessary, the government is also required to take quick action. It is therefore my duty to draw your attention to the fact that in the near future, it is possible to build a new type of bomb of great power. To this end, I suggest that you authorize someone you trust to communicate informally with various government agencies, report regularly to them on all studies, and provide them with advice, especially in trying to ensure the supply of uranium mines in the United States. At the same time, establish contact with relevant people and corporate laboratories to accelerate experimental work.? As far as I know, Germany has stopped selling ore from the Czech uranium mines it occupied. If you note that the son of Germany's undersecretary of foreign affairs works at the Kaiser Wilhelm Institute in Berlin, which is currently conducting the same research on uranium as the United States, it is not difficult to understand why Germany did this. Albert Einstein (Signed) Roosevelt silently studied Einstein's letter in the White House office and began to feel uncertain. But when he thought that Germany was stepping up its efforts to develop the atomic bomb, he secretly made up his mind. After a week of thorough consideration, he responded positively to the letter and issued instructions to conduct nuclear test research.