"Ellis Zacharias sipped on his dry martini as he matched poker skills with a group that included a young naval attaché with the Japanese embassy.

Zacharias, a naval intelligence officer posted in Washington in the 1920s, was not only playing poker

...but also trying to get the espionage-minded Japanese officer to let slip some information about his country's plans in the Pacific. He restricted himself to just the one martini in order to maintain his edge. This probing for information was a mutual exercise, usually...

..involving shrewd questioning by both men as they played each hand
Revealing only enough information to keep the conversation going, Zacharias could absorb what he heard over time while maintaining his friendship with the young Japanese officer, who had a reputation as a gambler

Some years later, Zacharias would use information gathered this way to warn his superiors that Japan, by then on the march across the Pacific Rim, would launch a surprise attack on the United States in the Pacific—on a Sunday morning. https://www.archives.gov/publications/prologue/2008/summer/zacharias.html

The Navy ignored his warnings. But early on December 7, 1941—a Sunday morning—Japan suddenly attacked Pearl Harbor, Hawaii. It was an operation planned by Zacharias's old poker-playing partner, Isoroku Yamamoto, by then commander in chief of the Japanese fleet"