The heads of the Soviet Union, the United States and Britain held talks in Potsdam. During a meeting break, President Truman told Stalin that the United States had developed a powerful bomb. This is to test Stalin's attitude towards the atomic bomb. Stalin didn't seem to hear it at all. He didn't show any unusual expression on his face and didn't give any answer, so that many people later recalled that Stalin seemed a little deaf and didn't hear clearly. In fact, Stalin heard clearly. After the meeting, he immediately said to Molotov, "We must speed up the work." Two years later, the Soviet Union successfully exploded the first atomic bomb, and the nuclear monopoly of the United States was completely broken.