What made the navajo code talkers so important to the u. s. war effort in the pacific?

Their language was so different and it could not be deciphered by the enemies because there was no way of understanding it.

They had such a complicated language that no one ever managed to crack it. So they could send all sorts of important messages from the base to the field and not worry about the enemy intercepting and using it against them. 

The russian empire, the french third republic, and united kingdom of great britain and ireland