Updated:
Original:
Year
1941

Japanese gather preliminary data on Pearl Harbor

On this day in 1941, the Japanese consul in Hawaii is instructed to divide Pearl Harbor into five zones and calculate the number of battleships in each zone—and report the findings back to Japan.

Relations between the United States and Japan had been deteriorating quickly since Japan’s occupation of Indo-China and the implicit menacing of the Philippines, an American protectorate. American retaliation included the seizing of all Japanese assets in the States and the closing of the Panama Canal to Japanese shipping. In September 1941, Roosevelt issued a statement, drafted by British Prime Minister Winston Churchill, that threatened war between the United States and Japan should the Japanese encroach any farther on territory in Southeast Asia or the South Pacific.

The Japanese military had long dominated Japanese foreign affairs. So, although official negotiations between the U.S. secretary of state and his Japanese counterpart to ease tensions were ongoing, Hideki Tojo, the minister of war who would soon be prime minister, had no intention of withdrawing from captured territories. He also construed the American “threat” of war as an ultimatum and prepared to deliver the first blow in a Japanese-American confrontation: the bombing of Pearl Harbor.

In September 1941, Nagai Kita, the Japanese consul in Hawaii, was told to begin carving up Pearl Harbor into five distinct zones and to determine the number of warships moored in each zone. Little did Japan know that the United States had intercepted the message; unfortunately, it had to be sent back to Washington for decrypting. Flights east were infrequent, so the message was sent via sea, a more time-consuming process. When it finally arrived at the capital, staff shortages and other priorities further delayed the decryption. When the message was finally unscrambled in mid-October—it was dismissed as being of no great consequence.

It would be found of consequence on December 7.

FACT CHECK: We strive for accuracy and fairness. But if you see something that doesn't look right, click here to contact us!

ALSO ON THIS DAY

Muhammad completes Hegira

On this day in 622, the prophet Muhammad completes his Hegira, or “flight,” from Mecca to Medina to escape persecution. In Medina, Muhammad set about building the followers of his religion–Islam–into an organized community and Arabian power. The Hegira would later mark the ...read more

The First Supreme Court

The Judiciary Act of 1789 is passed by Congress and signed by President George Washington, establishing the Supreme Court of the United States as a tribunal made up of six justices who were to serve on the court until death or retirement. That day, President Washington nominated ...read more

Ben Johnson wins gold, temporarily

On this day in 1988, Canadian sprinter Ben Johnson runs the 100-meter dash in 9.79 seconds to win gold at the Summer Olympics in Seoul, South Korea. Johnson’s triumph, however, was temporary: He tested positive for steroids three days later and was stripped of the medal. Ben ...read more

The “Chicago Seven” go on trial

The trial of the “Chicago Seven” begins before Judge Julius Hoffman. The defendants, including David Dellinger of the National Mobilization Committee to End the War in Vietnam (MOBE); Rennie Davis and Tom Hayden of MOBE and Students for a Democratic Society (SDS);and Jerry Rubin ...read more

A game warden is reported missing

Neil LaFeve, the game warden at Sensiba Wildlife Area in Wisconsin, is reported missing. When LaFeve, who was celebrating his 32nd birthday, did not show up to his own party, his wife called the police. The next morning, authorities found LaFeve’s truck. A pool of blood and two ...read more