Final answer:
Albert Einstein expressed his primary concern to President Franklin Roosevelt about the development of the atomic bomb, which was the possibility of Nazi Germany acquiring the weapon. He stressed the urgency of the United States initiating its own atomic bomb research to maintain a balance of power and ensure national security.
Step-by-step explanation:
Albert Einstein's primary concern that he raised to President Franklin Roosevelt about the development of the atomic bomb was the potential for the Nazi regime to obtain such a destructive weapon. Einstein, along with other scientists, feared that if Nazi Germany acquired the atomic bomb, they would have a significant advantage in World War II.
Einstein emphasized the urgent need for the United States to initiate its own atomic bomb research and development to prevent Nazi Germany from obtaining this devastating weapon first. He believed that developing the bomb was necessary to maintain a balance of power and ensure the security of the United States and its allies.
Einstein's letter to President Roosevelt, which led to the establishment of the Manhattan Project, expressed his concerns about the grave consequences of inaction and the need for immediate action to prevent potential catastrophe.
Learn more about Albert Einstein's concern about Nazi Germany acquiring the atomic bomb