In December 1944 he reported to Headquarters , Commander in Chief , US Fleet , Navy Department , and was assigned as his Assistant Chief of Staff ( Anti-Submarine ) , and Chief of Staff to the Commander , Tenth Fleet , serving under immediate direction of Fleet Admiral Ernest J. King . The Tenth Fleet , a fleet without a ship , was a highly specialized intelligence command , able to call upon the surface and air forces of the Atlantic Fleet and the Sea Frontier Forces as needed for special assignments , and was organized to exercise unity of control over the Navy 's war against U-boat operations in the Atlantic from Iceland to Cape Horn . The Tenth Fleet was dissolved in June 1945 , and Rear Admiral McCann was transferred to duty on the staff of the Commander in Chief , Atlantic Fleet , and was subsequently designated Commander , Task Force 68 , in the light cruiser during the Presidential trip to Berlin for the Potsdam Conference , July 4 , to August 8 , 1945 . He personally reported to President Harry S. Truman the news of the successful atomic bombing of Hiroshima , Japan
Potsdam Conference
Potsdam Conference
Allan Rockwell McCann