Carrier Pigeons
Pigeons have been used during war for over 2,000 years, proving effective at carrying messages for the Romans during battles. They were even used by both sides during World War I as a way to send messages between troops and commanders. A pigeon service was even created by the United States in 1917.
By the time World War II broke out, it seemed that pigeons were no longer needed. Advancements in radio communication and field phones meant that troops could coordinate over large distances and radio for help much faster than by sending a pigeon. But it was still not foolproof. Radio communications could be overheard and field phones were not always reliable.
Even in World War II pigeons proved their usefulness. They were able to communicate over long distances and communicate with troops who were not able to get messages through. In one instance British troops found themselves pinned down by German fire and unable to get to safety for nine days. In order to save them three scouts were sent along different routes, each with a homing pigeon. One scout was pinned down by fire while the other two were able to reach their destination. They sent details of their route by homing pigeon and the Allies were able to take the safe route in order to rescue the pinned troops.
All branches of the military continued to use pigeons as emergency communication throughout World War II. However, as technology continued to improve throughout the post-world war era, the need for pigeons was phased out. Today there are no pigeon units or uses for carrier pigeons in the military, however in the past they were responsible for saving countless lives.