LOUISVILLE, Ky. — The Navajo Code Talkers played crucial role in World War II, creating an "unbreakable code" that remains the only code unbroken by an enemy. It took decades before anyone knew they existed.

Of the 420 certified Navajo Code Talkers from the Greatest Generation, only two are alive today. If anyone could keep a secret, it was Peter MacDonald Sr. "Not even our parents knew what we did in the war," he said.

"The whole project was top secret." He was a boy living on a reservation in Arizona, who lied about his age to make the cut. "I volunteered to join the U.

S. Marine Corps at age 15, simply because my older cousin came home on furlough one day wearing that beautiful Marine Corps uniform," the 97-year-old veteran said. 'Not even a Navajo knows' At the time, MacDonald didn't know he'd be thrust into a top secret role that would help end the war.

The U.S. needed an unbreakable code, a language impossible for the enemy to decipher on the battlefield.

"Very smart, very intelligent enemy we had," MacDonald said, but they didn't know Navajo. The military's program started with 29 Navajo Marines. MacDonald said the Marines selected people from the Navajo Nation because it was the largest inland tribe in America.

That meant the program could suffer casualties, but still have the manpower to keep the baffling communication line going. "Not even a Navajo knows what in the world we're talking about," MacDonald said. Code Talkers could transmit and decode a three-line mess.