China's ancestors domesticated homing pigeons since ancient times and were called "flying slaves" in ancient times.
During the war between Xixia and Northern Song Dynasty, the Xixia army used homing pigeons for military communication. At the beginning of the Southern Song Dynasty, General Qu Duan's army also used homing pigeons to send messages and gather troops. Legend has it that when Liu Bang, the Emperor Gaozu, was surrounded by Xiang Yu, the overlord of Chu, he sent letters by carrier pigeons, which attracted reinforcements to escape from danger.
During the Han Dynasty, Su Wu was sent to Xiongnu, and Khan was exiled to feed sheep in Beihai. 10 years later, when the Han Dynasty approached the Huns, Khan refused to let Su Wu return to the Han Dynasty, so he and Su Wu sent a secret message to the Han envoy Su Wu, and designed the Han envoy to tell Khan that Emperor Xiandi shot a goose while hunting, and a letter was tied to the goose's foot, saying that Su Wu was herding sheep in a swamp. Khan told him after listening.