Yam (route)

Ögedei Khan gave special attention to Yam because Mongol armies travelled quickly; their messengers had to be even faster, and they covered 200–300 kilometres (120–190 mi) per day.

[2] As one of the most fundamental tools for managing the Mongol Empire, the operation of the Yam system was regulated by the written law Yassa.

This kind of support was made possible by the strict discipline within the empire, which also led to a high level of security, often described as Pax Mongolica.

[citation needed] The service has been described in great detail by European travellers including Giovanni da Pian del Carpine, William of Rubruck, Marco Polo, and Odoric of Pordenone.

While it was not the first messenger system in history (earlier ones existed in the Persian and Roman Empires), it was unprecedented in size and efficiency.