The tragedy that is the Pearl Harbor Attack, which occurred on December 7, 1941, made a significant impact on the United States—a literal turning point in American history.

The grim bombing raid in the harbor had been the fruit of extensive planning by the Japanese government and military, spending months on intelligence gathering, planning and coordination, training and rehearsals, deception, and intense strategy. During the day of the attack, they maintained radio silence to prevent movement detection and evade any interception.

Hiring spies and conducting reconnaissance missions helped ramp up the entire campaign by sending not only Japanese agents but also Nazi German into the unsuspecting island of Hawaii, among which was German national Bernard Julius Otto Kuehn.

Straight out of the Federal Bureau of Investigation (FBI)’s most famous cases, here’s how the intelligence agency caught Kuehn and his family red-handed.

A German Navy Veteran

According to official records, Otto Kuehn, born July 25, 1895, is the second of three children of German parents. The Kuehn’s lost their mother when Otto was 16, and a year after that, the young lad enlisted in the German Navy. One of his brothers also enlisted and participated in World War I.

Unfortunately, that brother would not make it through the battlefield alive. As his remaining brother pursued dentistry, Otto would later report that he became a prisoner of war—spending days on end in a British prison camp from January 1916 to November 1918, two years after his capture at sea.

Otto Kuehn
National Archives

After his release, Otto volunteered to clear mines from the North Sea in the Baltic. During the rise of the Third Reich, he became a member of the infamous Nazi Party, serving from 1928 to 1933.

Prior to his membership, Otto was attending medical school but had to drop out and give up two years-worth of education due to the hyperinflation experienced in 1920. Around this time, the German lad met and married his wife, Friedel Kuehn, which later would become his number one accomplice.