Before a single arrow was fired, Subutai had already won the information war. He knew the enemy's politics, geography, and morale better than they did.
Spies were sent 5-10 years in advance to map bridges, mountains, and political rivalries.
Merchants and diplomats acted as sleeper agents, feeding intelligence back to Mongolia via the Yam.
Information was calculated. Subutai knew the grain yields and population density of his targets.