PARIS (AP) — They were messengers, spies and sentinels. They led cavalry charges, carried supplies to the front, comforted wounded soldiers and died by the millions during World War I.

Horses, mules, dogs, pigeons and even a baboon all were a vital — and for decades overlooked — part of the Allied war machine.

Researchers have been hard-pressed to find official accounts of the services rendered by animals during the Great War. But if their labors once were taken for granted, four-legged and winged warriors have been acknowledged more recently as unsung heroes.

France recently decided to recogn...