Who first proposed the idea of using Native American languages for code talking?

The proposal to use Native American languages for code talking is credited to Philip Johnston. He was a World War I veteran and the son of a missionary who had grown up on the Navajo reservation. Johnston recognized the potential of Native American languages, particularly Navajo, to serve as a secure means of communication during military operations due to their complexity and uniqueness. He believed that the use of such languages would provide a tactical advantage as they were not widely understood or spoken by the enemy.

Johnston's idea led to the establishment of the Navajo Code Talkers during World War II, who developed an intricate code based on their native language. This code was pivotal in numerous battles in the Pacific theater as it allowed for secure communications that were indecipherable to enemy forces, significantly contributing to the success of military operations.

Other individuals mentioned in the options, like Jim Thorpe, Geronimo, and Thomas Jefferson, do not have documented connections to the concept of code talking in a military context or its implementation during the wars, making Johnston the key figure in this historical development.