(CNN)William Tully Brown, one of the last remaining members of the Navajo Code Talker program during World War II, died on Monday at age 96, according to the Navajo Nation.
Brown was one of about 400 Navajos who used their language to develop a code to transmit top-secret and confidential messages throughout World War II, says Peter MacDonald, president of the Navajo Code Talkers Association.
"From 1942 until 1945, Navajo code was used by the US Marines and Navy, and they tell us that we saved hundreds of thousands of lives and helped win the war in the Pacific to preserve our freedom and liberty," MacDonald said.
Brown was born in Black Mountain, Arizona, on October 30, 1922. He enlisted with the Marine Corps in 1944 and served until he was honorably discharged in 1946.
He was a member of the Navajo Code Talkers Association and worked on a project to launch a museum about the code talkers' work.
"We will always honor and remember the sacrifices he made at Guadalcanal and Iwo Jima in the protection of freedom and liberty," Navajo Nation Council Speaker Seth Damon said in a statement. "Mr. Brown's contributions to the Tselani/Cottonwood community and the Navajo Nation will always be cherished."
Brown is the third Navajo Code Talker to pass away in a month, the Navajo Nation said. Only five Navajo code talkers are still living, MacDonald said.
The Navajo Nation did not release the cause of death.
For his service, Brown received the American Campaign Medal, Asiatic-Pacific Campaign Medal, Navy Occupation Service Medal, World War II Victory Medal and Honorable Service Label Button.
How the code came to be
The Navajo code was indecipherable and crucial to American war efforts.
The system was much faster than the existing encryption machines at the time, according to the Office of the Director of National Intelligence. It was made of 211 vocabulary terms, but expanded to 411 over the course of the war.
The Navajo Code Talkers participated in every major Marine operation in the Pacific theater. During the battle for Iwo Jima, Navajo Code Talkers in the Marines successfully transmitted more than 800 messages, which proved critical to America's victory.
The idea to use the Navajo language to develop a code came from Philip Johnston, who spent most of his childhood on a Navajo reservation while his parents worked there as missionaries, the CIA said.
However, the Navajos' work wasn't recognized until after the US government declassified the operation in 1968. In 1982 President Ronald Reagan gave the Code Talkers a Certificate of Recognition and declared August 14 "Navajo Code Talkers Day" in 1982.
President Bill Clinton signed a law to award the Congressional Gold Medal to the original 29 code talkers, and President George W. Bush presented the medals to the surviving code talkers in 2001.
CORRECTION: An earlier version of this story incorrectly stated the number of Navajo code talkers still living. The headline and story have been updated.