On Dec. 8, 1941, Ensign Kazuo Sakamaki, the Japanese commander of a mini submarine, and his craft were captured on Bellows Army Airfield following the Japanese attack on Pearl Harbor. A map found within the sub revealed some surprises about the security of the Hawaiian Islands and the U.S. Navy’s Pacific Fleet.

The Japanese attack on Pearl Harbor was meant to be a two-prong aerial and submarine attack. More than thirty submarines were to take part, among them five two-person, 78-foot-long, mini submarines of the Special Attack Unit that were to enter the harbor quietly and fire on American ships berthed around Ford Island after the aerial attack began. One of these subs, I-24tou, was commanded by 24-year-old Lieutenant Sakamaki, who wrote in the ship’s log, “Today I will shoulder one important mission and, diving into Pearl Harbor, will sink the enemy’s warships.”

At 3:30 a.m., on Dec. 7, Sakamaki and Petty Officer Kiyoshi Inagaki launched their mini sub from its mother ship about ten nautical miles southwest of the entrance to Pearl Harbor. Sakamaki immediately noted several problems; most concerning were the sub’s malfunctioning gyrocompass and steering difficulties. Over the next few harrowing hours, Sakamaki and Inagaki veered way off course, hitting the coral reefs around the island of Oahu several times. At 8:17 a.m., the U.S.S. Helm discovered and fired on the sub; smoke and poisonous fumes rendered the crew unconscious. When Sakamaki came to and found the sub lodged on a reef, he ordered Inagaki to abandon ship while he set the self destruct charge and swam to shore.

The next morning, Soldiers of the Hawaii National Guard found a naked Sakamaki and his wrecked sub on Waimanalo Beach on the east coast of Oahu near Bellows Army Air Field. Sakamaki was turned over to the Federal Bureau of Investigation, which called in Army Capt. Gero Iwai, chief of the Translation Section of the local Counter Intelligence Detachment, and fellow Nisei Douglas Wada, a naval counterintelligence officer, to interrogate the captured Japanese officer. Sakamaki refused to cooperate, repeatedly but unsuccessfully requesting the means to kill himself. Three days later, the body of his crewmate, Inagaki, was recovered from the ocean.

Because the scuttle charge Sakamaki set failed to detonate, investigators poured over his sub and its contents. One key intelligence find was a copy of an American hydrographic chart on which were drawn the berthing locations of the U.S. Navy’s major warships and the locations of coastal guns. Upon further analysis of the map, Iwai and Wada also found Sakamaki’s planned route into Pearl Harbor and around Ford Island, along with anticipated times of arrival at several points along the route. This latter discovery was particularly troubling. Were the time notations along Sakamaki’s intended route an estimate or did they indicate the route had been reconnoited at an earlier date? Either conclusion pointed to serious flaws in the security of the harbor. A naval intelligence officer remarked, “All the necessary data to facilitate a submarine attack was in Japanese possession.” Military installations along the West Coast were immediately alerted to the potential for further attacks.

None of the five mini subs or their crews returned from their missions. Sakamaki was the sole survivor and the first Japanese prisoner of war captured by the Americans. He was sent to a prison camp at Camp McCoy, Wisconsin, and traveled to other camps to convince Japanese prisoners not to take their own lives. After the war, he returned to Japan and eventually became president of the Brazillian subsidiary of the Toyoto Motor Corporation. He died in Japan in 1991. His sub is on display at the National Museum of the Pacific War in Fredericksburg, Texas. The original map found in Sakamaki’s sub was stolen by a souvenir collector, fortunately after photostats were made.

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This piece is written by Senior Airman Akeem Campbell from the U.S. Army Intelligence Center of Excellence. Want to feature your story? Reach out to us at editor@sofrep.com.