The Navajo spoken code is not very complex by cryptographic standards, and would likely have been broken if a native speaker and trained cryptographers worked together effectively. The Japanese had an opportunity to attempt this when they captured Joe Kieyoomia in the Philippines in 1942. Kieyoomia, a Navajo Sergeant in the U.S. Army, was ordered to interpret the radio messages later in the war. They made no sense to him, and when he reported that he could not understand the messages, his captors tortured him. Given the simplicity of the alphabet code involved, it is probable that the code could have been broken easily if Kieyoomia's knowledge had been exploited more effectively by Japanese cryptographers.
The Imperial Japanese Army and Navy never cracked the spoken code, and high ranking military officers have stated that the United States would never have won the Battle of Iwo Jima without the secrecy afforded by the code talkers. The codetalkers received no recognition until the declassification of the operation in 1968. In 1982, the code talkers were given a Certificate of Recognition by President Reagan, who also named August 14 "National Code Talkers Day."
Kieyoomia says his captors at a Nagasaki prison initially tortured him because - judging from his surname - they thought he was Japanese-American.
"I told them I was Navajo," Kieyoomia says, his crystal-blue eyes turning defiant behind a wrinkled face and a pair of bifocals as he sat outside his remote home on the Navajo reservation and told his war story.
"They didn't believe me," he says, shaking his head. "The only thing they understood about Americans was black and white. I guess they didn't know about Indians."
After months of beatings, Kieyoomia says, the Japanese accepted his claim to Navajo ancestry. But he says the torture that followed was worse.
"One day two Japanese women visited me," he says. "They wrote Navajo words in English and asked what they meant. So, I told them: "This means bird, this means turtle, this means water."
Kieyoomia says he now thinks the Japanese were baffled after hearing the Navajo Code Talkers speak in their language, which was unwritten at the time. Unable to comprehend the sounds they turned to their captive Navajo.
The code, used by Navajo Marines to relay information across the Pacific, had the Navajo language as its basis, but developed a secret vocabulary in which armaments were renamed as everyday Navajo words.
When the Japanese questioned Kieyoomia his translations were useless.