The reasons why the U.S. military wanted to use the Navajo language as a code were:
It wasn't written down anywhere.
It was tonal.
It was complex.
<h3>Why was the Navajo language used?</h3><h3 />
The United States military were in need of a code that the Japanese would never be able to break and so they turned to the Navajo language for many reasons.
Some of these reasons were that it was a tonal language which was never written down so the Japanese would never see copies that would allow them to decipher the code. The language was also incredibly complex.
I believe when you say suffrage you are referring to the right to vote, so that means that the aristocrats had less power than before. Hope this helps :)