Why were Navajos not allowed to speak their native language for many years starting in
the 1860s?

The US wanted to force the Navajos and other Native American tribes to assimilate into American culture, so they tried to destroy their culture by making them not speak their language (until WWII, where they became the renowned Navajo Code Talkers)

Explanation:

It was technically genocide, since the US wanted to get rid of all Native American culture.

the answer is a new goverment.

the award is named for an american naval historian and theorist, rear admiral alfred thayer mahan, united states navy who, through his writing, provided stimulus and guidance to those who share in the defense of the nation.