Japanese Prime Minister Gen. Hideki Tojo took office just a month before the Pearl Harbor attacks, but had served as the Army minister for over a year before that and helped to draft the plan — from the attack at Pearl Harbor through the hopeful Japanese victory — for war with the western powers.
After Japan's surrender, Tojo knew that he would be arrested and executed. He attempted suicide on Sep. 11, 1945 as American soldiers moved into position around his house but he survived.
As Tojo awaited trial in 1946, the Navy sent Lt. j.g. Dr. George Foster, an oral surgeon, to examine the prime minister's heavily damaged teeth. The surgeon removed all but seven of Tojo's and then consulted with a Navy dental prosthetics officer, Lt. j.g. Dr. Jack Mallory.
Mallory recommended complete upper and lower dentures, but Tojo refused because he thought it would be a waste of effort to make both dentures for someone about to be executed. Instead, he asked for only an upper set of dentures so he could speak well at his trial.
Mallory and his friends devised a prank. They decided to engrave "Remember Pearl Harbor" on the back of the general's dentures. Knowing that he would get in trouble if caught, Mallory opted to engrave the message in Morse code instead of standard letters.
Only Foster and Mallory knew that Mallory had gone through with the joke.
You could see it clearly when it was dried, but 99 percent of the time you couldn't tell," Mallory told the Chico News and Review in 2002.
The secret got out though. Mallory bragged about the prank to two new members of the dental team and one of them told his parents in a letter. The parents passed the story on and it was broadcast on a Texas radio show.
When word began to circulate through Tokyo, Mallory went to his superior and confessed.
Army Maj. William Hill told the young dentist, "That's funny as hell but we could get our asses kicked for doing it."
Mallory and Foster knew a guard at the prison and got access to the prison on Feb. 14, 1947, to grind the message off of the dentures. Their mission was successful.
An Army colonel found out about the story the next morning and summoned the dentists to his office, but both men denied the rumors.
Tojo later complained that the dentures fit differently after they were adjusted that February night, but there are no signs that he ever knew about the trick the dentists played on him. He was sentenced to death during the trial and executed in 1948.
h/t Mental Floss.