Mongol hordes were ruthless when taking over a new territory. Iran's resistance required such force to subdue that much of the country's agrarian infrastructure was destroyed, causing famine and serious population loss in the years following the wars.
The Mongol Empire had benefits, however, to others as well as itself: an enforced peace throughout this realm made travel and trade safe for foreigners as well as residents. Given time, they might have conquered—and therefore united—North Africa and Europe as well. For the first time in their history, however, they were stopped, defeated when they encountered the Mamluks.
Hulagu, a grandson of Genghis and brother to Kublai and Möngke, managed the southwestern front of the Mongol Empire, moving from Persia toward Egypt. He took down the Assassins, and conquered Baghdad by defeating the Abbasid Caliphate. He then sent a message to Qutuz in Cairo, advising him to submit to Mongol rule. Qutuz killed the messengers and stuck their heads on one of Cairo's gates.
Then word came that Möngke Khan had died, and Hulagu took much of his army back home to lobby for the throne. When Qutuz learned that a much smaller military force had been left behind in the Middle East, he gathered his Mamluk army and marched out of Cairo. Two armies of about 20,000 men each met on 3 September 1260 at Ain Jalut ["Spring of Goliath"] in Galilee.
The Mongol army did not know the territory as well as the Mamluks did (Qutuz had allied himself with a Mamluk leader from the region who knew it well and planned their strategy). The Mamluks played a "hit-and-run" game, then pretended to retreat, luring the Mongol army to follow them into the highlands where the largest part of the army was hidden, its archers waiting to ambush the Mongols. Although the Mongols rallied somewhat, they were unable to gain the upper hand. For the first time, their forward advance to expand their territory was stopped, placing a western border in the face of Genghis Khan's dream of a worldwide Mongol empire.
The Mamluks had another advantage: explosives, specifically hand cannons. Hand cannons were metal cylinders packed with gunpowder and set off with a flame. They were not good for aiming projectiles with any kind of accuracy, but in the Battle of Ain Jalut they were used to startle the opposing cavalry mounts and create confusion.