Empire of Grass: The Conquests of Genghis Khan

From BoardGameGeek:

Solitaire game of the Mongol invasion of Eurasia in the twelfth century under Genghis (Chinggis) Khan. You play the Great Khan, commanding his armies as he conquers territories, recruits other nomads into his army, and either garrisons or razes cities. The map of your conquests is made through placing cards which represent the regions of Eurasia that the Mongols conquered (or tried to). As you expand you have to take care as neighbouring kingdoms may appear to challenge you and your allies can desert or even rebel. An optional game allows for an uncertain world with the cards randomised. -description from the designer