During the war in the Pacific, the U.S. Marines recruited 29 Navajo men to create an unbreakable code based on their complex, unwritten language. They developed a dictionary of over 200 terms, using Navajo words for birds or fish to represent planes and ships (e.g., 'iron fish' for submarine). Unlike previous codes, this was a 'living code' that could be transmitted instantly by voice. The Japanese, who were master code-breakers, were never able to decipher it. At Iwo Jima alone, six Navajo talkers worked 24 hours a day, sending over 800 messages with perfect accuracy. Major Howard Connor stated, 'Without the Navajos, the Marines would never have taken Iwo Jima.'