 Under the 1943 Quebec Agreement with the United Kingdom, the United States had agreed that nuclear weapons would not be used against another country without mutual consent. In June 1945 the head of the British Joint Staff Mission, Field Marshal Sir Henry Maitland Wilson, agreed that the use of nuclear weapons against Japan would be officially recorded as a decision of the Combined Policy Committee. At Potsdam, Truman agreed to a request from Winston Churchill that Britain be represented when the atomic bomb was dropped. William Penney and Group Captain Leonard Cheshire were sent to Tinian, but found that LeMay would not let them accompany the mission. All they could do was send a strongly worded signal back to Wilson.
