Into Azerbaijan, Armenia and Eastern Europe

While Genghis Khan was consolidating his conquests in Persia and Afghanistan, a force of 40,000 Mongol horsemen pushed through Azerbaijan and Armenia. They defeated Georgian crusaders, captured a Genoese trade-fortress in the Crimea and spent the winter along the coast of the Black Sea. As they were headed back home they met 80,000 warriors led by Prince Mstitslav of Kiev. The battle of Kalka River (1223) commenced. Staying out of range of the crude weapons of peasant infantry, and with better bows than opposing archers, they devastated the prince's standing army. Facing the prince's cavalry, they faked a retreat, drawing the armored cavalry forward, taking advantage of the vanity and over-confidence of the mounted aristocrats. Lighter and more mobile, they strung out and tired the pursuers and then attacked, killed and routed them.
In 1225, Genghis Khan returned to Mongolia. He now ruled everything between the Caspian Sea and Beijing. He looked forward to the Mongols benefits of caravan trade and drawing tribute from agricultural peoples in the west and east. He created an efficient pony express system. Wanting no divisions rising from religion, he declared freedom of religion throughout his empire. Favoring order and tax producing prosperity, he forbade troops and local officials to abuse people. Soon again, Genghis Khan was at war. He believed that the Tangut were not living up to their obligations to his empire. In 1227, around the age of sixty-five while leading the fighting against the Tangut, Genghis Khan, it is said, fell off his horse and died.
In terms of square miles conquered, Genghis Khan had been the greatest conqueror of all time -- his empire four times larger than the empire of Alexander the Great. The Mongol nation believed that he had been the greatest man of all time and a man sent from heaven. Among the Mongols he was known as the Holy Warrior, and not unlike the Jews, who continued to see hope in a conquering king (messiah) like David, Mongols were to continue to believe that one day Genghis Khan would rise again and lead his people to new victories.