JF Ptak Science Books Quick Post
This is document 63 of 80 from "The Atomic Bomb and the End of World War II, a Collection of Primary Sources", from the National Secuiry Archive Electronic Briefing Book No 162, edited by William Burr (2005). (The full source is available here.) It is here where there is a brief review of supposed Japanese development of an atomic bomb. the information was courtesy of the MAGIC, a cryptonym for the successful effort of the United States Army Signals Intelligence Section (SIS) and the Navy Communication Special Unit to decode intercepted high-level Janapese messages. (A quick appraisal of MAGIC is available here.) Suffice to say for this quick post that the efforts of American cryptographers (with some help from our cousins in the U.K. at Bletchley Park) landed the U.S. the ability to read and render Japanese critical and encoded communications virtually from the very beginning of the war.
Read more: http://www.faqs.org/espionage/Nt-Pa/Operation-Magic.html#ixzz2OPnQy4oJ