One of the foremost advantages the Allies had during the Second World War was the United States’ Navajo Code Talkers. Because Native American tribes developed language and culture separately from Europe and Asia, there was no basis for the German cryptographers to begin to decrypt their codes. An extra layer of encryption was that the Navajo code corresponded to words or letters in the English language, rather than their own meanings, which made decryption more than simply understanding the Navajo language (which the Germans and Japanese were unable to do, anyway).
Though German forces were overly confident in the Enigma cipher and its complexity and impermeability, it did not mean they were unable to gain ground with cracking the Allies’ ciphers. Codes and cipher machines such as Type X and SIGABA may have been more effective than Enigma because Allied cryptographers were more careful than German ones. However, there was always a risk that the German cryptanalysts had begun to crack the codes, and decrypting the messages sent by those machines were also very slow. Implementing the Navajo Code Talkers made it basically impossible for the Germans to crack the code, and also expedited the process of sending and deciphering messages that greatly contributed to the Allies’ victory.