In a bit of pre-planning, the Japanese Foreign Office alerted its overseas personnel to a method of getting information if the communications between them and the home country were cut off by the hosting nations. Much has been made about a possible signal being sent regarding US-Japanese relations being "not as expected", ("East Wind Rain" in the Winds code). The Investigations into the attack examined this matter and found, most importantly, that the conditions that would cause implimentation of the code were never in place before the attack. The link below will allow you to read the original text of the "Winds" message and commentary on it.
MATERIAL RELATING TO "WINDS" CODE