In 1942 while the British were working on cracking the Nazi code at Bletchley Park, the Americans were using a language that was completely foreign to those who were not familiar with it. At the time the Navajo language had NO written alphabet, so it was almost impossible to decrypt. The Native American Navajo language was detrimental to the success of translating important information from person to person on the battlefield for the Americans. This is why the US Military enlisted individuals who were native  Navajo speakers to help translate the code.