The first atomic bomb test by the Soviet Union in August 1949 came earlier than expected by Americans, and McMahon immediately urged that U.S. production of atomic weapons be substantially increased. Moreover, during the next several months there was an intense debate within the U.S. government, military, and scientific communities regarding whether to proceed with development of the far more powerful hydrogen bomb, then known as "the Super". McMahon was strongly in favor of going ahead with the Super, and argued as much in a series of letters he wrote to President Truman. The senator rejected morality-based arguments against the hydrogen bomb based on it being inherently more destructive than previous weapons, asking "Where is the valid ethical distinction between" the World War II multi-day-and-night bombing of Hamburg, the firebombing of Toyko, and the atomic bombing of Hiroshima, and any future raid with whatever technology that caused mass casualties.