using a character code. nine characters and a period. they stopped using that code completely and started using a five digit code which the navy promptly named jm 25. >> oliver: to maintain security, yamomodo changed the code. even with the number of people that we had there was no way that could have been broken in time to read anything prior to pearl harbor. >> oliver: "war stories" investigates tracked down boris who remembers that august of '41 was a strange time in jo pan. he had been living in tokyo for go years as part of a special u.s. navy program. >> the naval at the embassy sent a message to washington saying they should go. we you saw the war coming on. >> oliver: but there was one problem. the japanese refused to let him and his colleagues leave. the young officer watched in surprise as the beautiful wife