Kii Yázhí was given the name Ned Begay because the white man giving out names thought Begay was his father's last name. In reality, Begay means "son of" so lots of Navajos are now named Begay because of ignorant white men.
Ned would grow up to join the Marine Corp and become a code talker. Ned fought on many Pacific Islands, but his main job was using the Navajo language to confound the Japanese. The same language he was forbidden to speak as a boy. Ned and his fellow Navajos were very good at their job. That's what this book is all about. Very highly recommended.