Philip Johnston was not a Navajo man.

He was the son of a Protestant missionary who had spent years on the Navajo Nation, and he had grown up alongside Navajo children, learning the Diné language in the informal, immersive way that children learn languages — not from a textbook but from daily life.

By adulthood, he was one of a very small number of non-Navajo people who had genuine fluency in Diné Bizaad.

Johnston was also a civil engineer who had served in World War I and had some understanding of the military communications problems that modern warfare created.

When he read accounts of the early Pacific war and thought about the communications challenge the Marines faced, he made a connection that was, in retrospect, obvious — but that required his specific combination of experiences to see.

Diné Bizaad, the Navajo language, was extraordinarily difficult for outsiders to learn.