World (and personal) history often turns upon single, critical events determined by minor perturbing influences. WW 2.5 explores the effects upon history of a minor malfunction preventing the bomb dropped upon Hiroshima from detonating, placing in the hands of the Japanese a nearly intact weapon suitable for threatening those powers that were on the brink of attacking its home islands. The resulting thoughts and actions of the crew of the Enola Gay delivery plane, President Truman, General Groves, General McArthur, Robert Oppenheimer, Los Alamos scientists, the Japanese Imperial Diet and military, Hirohito, American fighting men en route from the European theatre to Japan, a treacherous American Senator, etc. are brought into play as they affect the course of World history.