[brazzy]

> Genghis had the advantage that his tanks ate grass, and grass grew everywhere the Mongols decided to conquer.

More like: wherever you didn't have abundant grass, Mongol armies essentially couldn't go, or at least lost so much advantage that they usually chose not to.

On a related point: the southern half of Ukraine has some of the best soil in the world for agriculture, yet for centuries it was very thinly populated and called the "Wild Fields", because it's naturally steppe and living there put you in reach of the Crimean Tartars, descendants of the Mongols who also used the same tactics for devastating raids. Further north, where the land was covered in forest, they did not go.

> That said, they still specifically timed their campaign cycles around the availability of forage in the country to be attacked.

Everyone did that (had to) back then.