Most of the major campaigns took place in predominanantly prarie ecosystems. Almost everywhere the armies went was surrounded by fields of grass and grains. The mobility of the army allowed almost constant movement to find new fodder for the animals, and driving livestock along with the army allowed the soldiers to eat meat and milk consistently through a campaign. In a pinch they would even drink blood from the horses they rode to sustain themselves on forced marches where they couldn't afford to stop. The Mongol armies used their ability to deploy quickly and move almost constantly as their main strategy. Almost as soon as they hit continuous forest or mountains they would change course.