The Mongols built a horse-relay network that moved mail 200 miles a day

Genghis Khan and Ogedei Khan built the Yam, a chain of relay stations roughly 20-40 miles apart across the empire, stocked with fresh horses, food, and shelter for couriers. Riders swapped exhausted mounts at each stop and could cover 200-300 miles in a single day. Marco Polo marvelled at the network, which by the late 13th century used hundreds of thousands of horses across thousands of stations.

— Jack Weatherford, Genghis Khan and the Making of the Modern World — 2004; chapter on Mongol communications (the Yam relay system)
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