There was no room for error in a maneuver like that. The old Shackle communications system took so long to encode and decode, and it was so frequently inaccurate, that using it for the transmission of on-the-fly target coordinates was a perilous proposition. Frequently, in the midst of battle, instead of using the Shackle code, the Marines had transmitted in English. They knew the transmissions were probably being monitored by the japanese, so they salted the messages liberally with profanity, hoping to confuse the enemy.

On Guadalcanal the US Marines were still dug in fending off Japanese attacks on their positions around Henderson Field. A remarkable new asset joined them in November 1942, when a detachment of Marines recruited from the Navajo Nation arrived. It was becoming necessary to communicate urgently by wireless on the battlefield – yet the Marines had learnt that the Japanese were often listening in. The introduction of men speaking in Navajo was to transform this situation. Chester Nez was one of the men who joined the battlefield in November 1942:

A runner approached, handing me a message written in English. It was my first battlefield transmission in Navajo code. I’ll never forget it. Roy pressed the transmit button on the radio, and I positioned my microphone to repeat the information in our code. I talked while Roy cranked. Later, we would change positions. “Beb-na-ali-trosie a-knah-as-donih ab-toh nish-na-jih-goh dah-di-kad ah-deel-tahi.” Enemy machine-gun nest on your right flank. Destroy. Suddenly, just after my message was received, the Japanese gun exploded, destroyed by U.S. artillery.

One of the characteristics of the Navajo language was its oral tradition. The men were accustomed to remember quite long and detailed instructions rather than writing them down. This was to be an important aspect of the Navajo Code talkers work in addition to the fact that they their communications were impenetrable to the Japanese. Under the stress of combat conditions they were able to remember and pass on detailed instructions quickly without writing them down:

The hilly terrain on Guadalcanal posed real problems for the men operating mortars and artillery. Muzzle-loaded mortars were low-velocity, short-range weapons with a high trajectory, particularly well suited to uneven terrain. A mortar could drop into an enemy trench that artillery fire flew right over. Shells fired by field artillery reached a higher velocity and followed a flatter trajectory. Howitzers were similar to mortars in function, but larger. The men firing all of these weapons dealt with a serious issue. Artillery, howitzers, and mortars targeted an enemy who was frequently nose to nose with the American soldiers at the front. Marksmen had to clear the hills and the heads of our own troops, causing them no injury, while drawing an accurate bead on the enemy. This became especially ticklish when we were “walking fire in.” ‘That meant that our weapons were shooting behind the enemy and drawing them closer to the American troops at the front line. As they drew closer, we continued to fire behind them, moving both our fire and the Japanese troops closer and closer to our own troops. There was no room for error in a maneuver like that. The old Shackle communications system took so long to encode and decode, and it was so frequently inaccurate, that using it for the transmission of on-the-fly target coordinates was a perilous proposition. Frequently, in the midst of battle, instead of using the Shackle code, the Marines had transmitted in English. They knew the transmissions were probably being monitored by the japanese, so they salted the messages liberally with profanity, hoping to confuse the enemy. We code talkers changed all that.

See Chester Nez: Code Talker .