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On 19 November 1941 the Japanese Foreign Ministry sent messages to various consulates and embassies using J-19 code. The message, #2353, said that, given the poor situation in diplomatic relations, communications might be severed at any time and codes and decoding machines should be the subject of "action" by the relevant missions if they were given a warning in the form of a weather report at the end of overseas news broadcasts. A Japanese-American crisis would be indicated by the words Higashi no kaze ame (east wind rain), Japanese-Russian by Kita no kaze ku-mori (north wind cloudy), Japanese-British, including the invasion of Thailand or an attack on Malaya or the Netherlands East Indies by Nishi no kaze hare (west wind clear). As J-19 could be read by the British, Americans, French and Dutch, it was hardly a secret at all. However, the code was time-consuming to translate and the Americans did not complete the task until 28 November. On that day Commander Laurence F. Safford of the Naval Communications Service in Washington instructed his intercept stations to monitor Japanese broadcasts accordingly. "East wind rain" was picked up in the middle of a 200-word weather forecast at Cheltenham, Maryland on 1 December and sent to Safford's OP-20-G unit the next day. It was then circulated to army and navy departments, but not, apparently, outside mainland USA. Whether it conveyed more information than an intelligent monitoring of everyday diplomatic relations at the time is open to question.

See also: espionage; J-19