First World War carrier pigeon signaller. US soldier holding a pigeon being used to carry military messages during the First World War (1914-1918). The message is being attached to the pigeon's leg. Carrier pigeons were extensively used by all sides during this war, carrying messages from the frontline back to headquarters as soldiers advanced beyond the pre-laid telephone networks. Pigeons were used because radio communications were not yet fully developed or reliable enough. Over 100,000 carrier pigeons were used during the war, with only a 5% failure rate. This soldier is in the US Army's Signal Corps. The US entered the war on 6 April 1917, playing a crucial role in helping Britain and France to defeat Germany and its allies. Photographed between 1917 and 1918.