The code operated on two levels, and understanding both levels is essential to understanding why it was effective.

The first level was a military vocabulary.

Navajo did not have words for many modern military concepts — aircraft, tanks, battleships, specific military ranks, tactical terminology.

The Code Talkers developed Navajo equivalents for these concepts using a system of descriptive naming that was both logical and memorable.

An airplane was called by the Navajo word for bird, with different birds indicating different types of aircraft: a fighter plane was called a hummingbird, a torpedo plane was called a swallow, a bomber was called a buzzard.

A battleship was called iron fish.