 Until its declassification in 1968, the code that these Navajo developed remains the only oral military code that was not broken by an enemy.The code itself was composed of carefully-selected Navajo words that used poetic circumlocution so that even a Navajo-speaker would not be able to understand the communications without training.For example, since there were no words in Navajo for military machines, weapons, or foreign countries, so these words were substituted with words that did exist in the Navajo language.