Final answer:
The atomic bomb was developed after German physicists discovered nuclear fission in 1938. Albert Einstein warned the U.S. about this, leading to the Manhattan Project, which resulted in the Trinity test in 1945 under J. Robert Oppenheimer. Espionage activities, including those by Klaus Fuchs and the Rosenbergs, affected the post-war atomic landscape.
Step-by-step explanation:
Discovery of the Atomic Bomb
The groundwork for the atomic bomb was set when German physicists Otto Hahn and Fritz Strassmann accidentally discovered nuclear fission in December 1938. Following this discovery, Germany started a secret program known as the Uranium Club to create an atomic bomb. Concerned by these developments, Albert Einstein—a German-born physicist who had emigrated to the United States—sent a letter to President Roosevelt, which had been penned by fellow physicist Leo Szilard, warning of the potential for a German atomic bomb and suggesting an increased effort in atomic research by the U.S.
The United States responded with the Manhattan Project, a secret and ambitious program that began in 1942, involving a considerable mobilization of resources and personnel. This led to the successful detonation of the world's first nuclear device, known as 'Trinity', in New Mexico in July 1945, under the leadership of physicist J. Robert Oppenheimer. During this time, other nations, including Germany and Japan, also aimed to develop atomic bombs but faced setbacks due to various challenges.
The atomic bomb's development was hastened by the espionage activities of individuals like Klaus Fuchs who, after being apprehended in 1950, admitted to sharing atomic secrets with the Soviets, which allowed them to advance their own nuclear program. The revelation of such espionage activities caused concern and led to subsequent arrests, notably of Julius and Ethel Rosenberg in the United States.