It has remained one of World War II’s most enduring mysteries, one that resonated decades later after Sept. 11: Who in Washington knew what and when before the Japanese attacked Pearl Harbor on Dec. 7, 1941?

Specifically, who heard or saw a transcript of a Tokyo shortwave radio news broadcast that was interrupted by a prearranged coded weather report? The weather bulletin signaled Japanese diplomats around the world to destroy confidential documents and codes because war with the United States, the Soviet Union or Britain was beginning.

In testimony for government inquiries, witnesses said that the “winds execute” message was intercepted as early as Dec. 4, three days before the attack.

But after analyzing American and foreign intelligence sources and decrypted cables, historians for the National Security Agency concluded in a documentary history released last week that whatever other warnings reached Washington about the attack, the “winds execute” message was not one of them.