In this episode of Fexingo History, Lucas and Luna explore the Mongol Empire's extraordinary communication network—the yam system. From Chinggis Khan's early couriers to the vast relay networks that stretched from Karakorum to Dadu, Sarai, and Tabriz, they uncover how this postal web held the largest contiguous empire in history together, and how its very efficiency accelerated its fragmentation. Along the way, they meet the men who rode the harsh steppe routes, the paizi—the golden tablets that gave them passage—and the merchants who exploited the system, often at the empire's expense. They also touch on the accounts of Marco Polo and William of Rubruck, whose journeys were made possible by these very routes, and the administrative brilliance of Juvayni. But the yam was more than a postal service—it was a tool of control, a lifeline for armies, and a symbol of imperial reach. Yet as the empire fractured, the yam became a double-edged sword, enabling rapid communication between rival khans and fueling the very rivalries that tore the Mongols apart. Tune in for a fresh angle on the Mongol Empire's rise and fall, through the lens of its messengers.