Starting with World War One, most of the major militaries began to use homing pigeons to carry messages back from the front lines. Much lighter than a radio set and more mobile than a telephone connection, pigeons were a surprisingly practical way of sending messages. One American pigeon, Cher Ami, even won the Croix de guerre for delivering several important messages despite suffering serious injuries from enemy fire. (You can see him, along with other “hero pigeons,” on display at the Smithsonian.)
Between the wars, most nations preserved their carrier pigeon programs. In the US, the Army Signal Corps kept roughly 300 pigeons on hand for training while planning to breed 1,000 pigeons a month in wartime. During World War Two, the British provided hundreds of thousands of pigeons to spies, special forces, aircrew, and other military units. The Americans used 54,000, 40,000 of them donated by civilian breeders. The pigeon programs lasted beyond the war, with US Army pigeons serving in Korea. The American Pigeon Breeding and Training Center at Fort Monmouth only closed in 1957.
Of course, where there were pigeons there were anti-pigeon countermeasures. In 1941, Fort Monmouth reported to the New York Times that troops there were training at least one falcon, named “Thunderbolt,” to hunt enemy pigeons. Some sources say that Thunderbolt was equipped with sharpened metal claws to aid him in his task.
Despite a promising start, the American anti-pigeon program never got off the ground. But, according to MI 5 records declassified in 1999, the British did release birds of prey to hunt pigeons suspected of carrying messages from Nazi spies. The British falcons apparently managed to capture two Nazi birds; the officer in charge of the case reported that “Both birds are now prisoners of war working hard at breeding English pigeons.”*
* I have my doubts about whether those two birds were really Nazi messenger pigeons. By mid-1942, when they were caught, there were no German intelligence agents still loose in Britain. Of course, that fact was a closely-held secret, so the MI 5 officers in charge of the anti-pigeon program would have had no way of knowing there were no enemy birds to catch.