Navajo Code Talkers

Please write an essay involving the Navajo Code Talkers and their contributions to WWII. The topic should be as narrow as possible but cover specifically how the code talkers made an impact on the battles and their contributions to the war efforts.
Primary and secondary resources should be used, but the primary sources should be pulled from sites such as:
LOC.GOV ( Library of Congress)
NARA.GOV ( National Archives)
SI.EDU ( Smithsonian Institute)
Formatting should be in Chicago Style with footnotes on the bottom of each page.