This command structure was highly flexible and allowed the Mongol army to attack en masse, divide into smaller groups to encircle their enemies and either lead them into an ambush or divide into small groups of roughly 10 to mop up a fleeing and broken army. The leaders on each level had significant license to execute their orders in the way they considered best. Transfer of troops between units was forbidden. In many cases, the Mongols defeated significantly larger armies. Foreign technical experts were integrated into the command structure. Technologies useful for attacking fortifications were adapted from other cultures. Other elements were invented by Genghis Khan, his generals, and his successors. That system was founded originally on the expansion of the nomadic lifestyle of the Mongols. The Mongolians military tactics and organization enabled the Mongol Empire to conquer nearly all of continental Asia, along with parts of the Middle East and Eastern Europe.