"How did they conquer without leaving a standing army? If they were so brutal then those left behind would revolt, eventually."
From the "Mongol invasion of Khwarezmia"¹ about cities which opposed resistance:
1. Otrar - "Genghis killed many of the inhabitants, enslaved the rest"
2. Bukhara - "Survivors from the citadel were executed, artisans and craftsmen were sent back to Mongolia, young men who had not fought were drafted into the Mongolian army and the rest of the population was sent into slavery."
3. Samarkand - "After the fortress fell, Genghis reneged on his surrender terms and executed every soldier that had taken arms against him at Samarkand. The people of Samarkand were ordered to evacuate and assemble in a plain outside the city, where they were killed and pyramids of severed heads raised as the symbol of Mongol victory."
4. Urgench - "As usual, the artisans were sent back to Mongolia, young women and children were given to the Mongol soldiers as slaves, and the rest of the population was massacred."
5. Gurjang - "Upon its surrender the Mongols broke the dams and flooded the city, then proceeded to execute the survivors."
6. Merv - "Tolui slaughtered almost every person who surrendered, in a massacre possibly on a greater scale than that at Urgench."
7 Nishapur - "Tolui put to the sword every living thing in city"
Then an outlier:
"After Nishapur's fall, Herat surrendered without a fight and was spared."
From the "Mongol invasion of Khwarezmia"¹ about cities which opposed resistance:
1. Otrar - "Genghis killed many of the inhabitants, enslaved the rest"
2. Bukhara - "Survivors from the citadel were executed, artisans and craftsmen were sent back to Mongolia, young men who had not fought were drafted into the Mongolian army and the rest of the population was sent into slavery."
3. Samarkand - "After the fortress fell, Genghis reneged on his surrender terms and executed every soldier that had taken arms against him at Samarkand. The people of Samarkand were ordered to evacuate and assemble in a plain outside the city, where they were killed and pyramids of severed heads raised as the symbol of Mongol victory."
4. Urgench - "As usual, the artisans were sent back to Mongolia, young women and children were given to the Mongol soldiers as slaves, and the rest of the population was massacred."
5. Gurjang - "Upon its surrender the Mongols broke the dams and flooded the city, then proceeded to execute the survivors."
6. Merv - "Tolui slaughtered almost every person who surrendered, in a massacre possibly on a greater scale than that at Urgench."
7 Nishapur - "Tolui put to the sword every living thing in city"
Then an outlier:
"After Nishapur's fall, Herat surrendered without a fight and was spared."
Now, let's see... who wants to revolt?
¹ http://en.wikipedia.org/wiki/Mongol_invasion_of_Khwarezmia_a...