Flying aces in their warplanes were not the only air force that took flight during World War I. As many as 500,000 homing pigeons accompanied soldiers, sailors and pilots into battle, delivering military intelligence and distress messages that saved thousands of lives. Some birds earned hero status for fulfilling their missions—even after being gravely injured. “Cher Ami,” for one, received the French military’s highest honor. “President Wilson” is enshrined at the Pentagon.

The First World War ushered in the battlefield use of the radio and telephone, but these new technologies proved unreliable in trench warfare. Artillery bombardments and sabotage easily severed wires leading from the trenches. And signalers hauling large coils of wire made easy targets for snipers.

When modern communication methods failed, militaries turned to time-tested homing pigeons to navigate bombardments, smoke and poor weather. Capable of flying 60 miles per hour while traveling 500 miles or more in a day, these diminutive battlefield messengers had been valued for their speed, endurance and extraordinary navigation skills since antiquity. Dr. Christopher Warren, vice president and senior curator of the National World War I Museum and Memorial, says armies had a 95 percent success rate in delivering messages by pigeons. “Pigeons were one of the most reliable forms of communications. While newer forms of communication could break, pigeons were doing the thing they were doing for 2,000 years.”

Elizabeth G. Macalaster, author of War Pigeons: Winged Couriers in the U.S. Military, 1878-1957, says scientists generally believe these birds’ uncanny ability to navigate back to their homes comes not only from keen eyesight. They also have magnetite in their beaks that could act as a compass and an extraordinary ability to detect low frequency noises that travel long distances and guide them home. “Despite all of this knowledge,” she says, “the exact mechanisms by which homing pigeons navigate home from a place they’ve never been remain a mystery.”

When World War I erupted in 1914, both sides poured resources into developing feathered arsenals. In October 1914, the British Army commissioned Lieutenant Colonel Alfred Henry Osman, founder of Racing Pigeon magazine, to create the Army Pigeon Service. Using his extensive contacts, Osman persuaded pigeon breeders to donate birds and join the service, recruiting 100,000 pigeons for Britain’s war effort.

To facilitate rapid delivery of messages from the trenches, the French successfully experimented with breeding birds in mobile lofts fashioned from horse-drawn carriages and double-decker buses. Installed in lofts five weeks after hatching, young pigeons were handled daily to become comfortable with humans. Initially, handlers released them a few hundred feet from their lofts and gradually increased distances to upward of four miles. Advanced training entailed shifting mobile lofts from location to location. After 10 weeks, pigeons were ready for short flights from the trenches to lofts placed a few miles behind the front lines.

Marching into the trenches with rifles and baskets of pigeons on their backs, soldiers wrote messages on fine tissue paper that they folded and inserted into small aluminum cylinders attached to the birds’ legs. At least two birds carried the same message to increase the odds of delivery. Returning to their lofts, pigeons entered through openings that rang bells to notify pigeon masters of messages.

Pigeons served in every military branch. Tanks dispatched pigeons to relay locations of hidden machine gun nests. Pilots launched them midair to transmit reconnaissance information as quickly as possible. Ships and seaplanes traveled with pigeons to send distress calls in the event of radio failure or emergencies. In Britain alone, more than 700 pigeons relayed messages from sinking ships and planes downed at sea that facilitated their rescues.

As homing pigeons became valuable weapons for the Allies, the Germans deployed sharpshooters and more natural predators—falcons—to remove them from the skies. French forces countered by dyeing pigeons black to camouflage them as crows.

When the American military entered World War I in 1917, it had little experience using homing pigeons apart from unsuccessful experiments during the Spanish-American War and the 1916 expedition to capture Pancho Villa in Mexico. “Once they saw from the British and French how useful these pigeons could be, the Americans start a pretty robust training program,” Warren says.

Homing pigeons completed nearly 11,000 wartime flights for the U.S. Navy, the first American military branch to use the birds as messengers. The U.S. Army Pigeon Service, which launched operations in France in March 1918, was staffed by 330 “pigeoneers” tasked with caring for and training the birds. Doughboys unfamiliar with pigeons received a five-day crash course in how to handle them and transmit messages. In addition to purchasing 10,000 pigeons from American fanciers, the Pigeon Service received 600 birds donated by the British, including one of wartime’s most famous animals.

That bird, named Cher Ami, had already demonstrated valor by delivering messages for French forces at the Battle of Verdun. But its most famous mission came in October 1918, when it accompanied America’s 77th Infantry Division in the massive Meuse-Argonne Offensive. While attacking a heavily fortified German line in northern France, 554 soldiers advanced too far and became trapped in a ravine where they weathered repeated enemy attacks along with incoming friendly American artillery fire.

Legend has it that, with all other means of communication cut off, the desperate doughboys faced annihilation with their one remaining pigeon their only hope of survival. U.S. Army Major Charles Whittlesey frantically scribbled a note that he folded inside a cannister attached to Cher Ami’s leg. As the division watched Cher Ami take flight, a German gunner blasted the pigeon from the sky. Incredibly, the wounded bird struggled back into the air and flew 25 miles back to the American base.

Cher Ami arrived blinded in one eye, with a deep wound across his chest and a canister dangling from what was left of his right leg. Inside was the message: “We are along the road parallel to 276.4. Our own artillery is dropping a barrage directly on us. For heaven’s sake, stop it!” The coordinates aided with the eventual recovery of the “Lost Battalion,” saving 194 American lives.

The pigeon, whose leg required amputation, became an American hero. “Cher Ami symbolized the heroic nature of animals during World War I, the last war in which animals still played such an extensive role,” Warren says. The French government awarded the feathered combatant its highest military honor: the Croix de Guerre, with palm. Grateful members of the Lost Battalion crafted a tiny wooden leg for him.

“There isn’t anything the United States can do too much for this bird,” said John J. Pershing, commander of the American Expeditionary Force. Under Pershing’s orders, Cher Ami sailed to the United States after the war, where he lived in retirement in a pigeon loft in Washington, D.C. After he died in June 1919 from his battle wounds, Cher Ami’s taxidermied remains were mounted for display in the Smithsonian as a lasting reminder of pigeons’ World War I contributions.