Generally, from that time on, division appeared among the Mongols. Genghis Khan had advised his sons to maintain agreement and unity, saying, “So long as you agree with each other, fortune and triumph will be your friends, and no opponent can achieve victory.” It was through this quality that it was possible for him and his offspring to conquer most of the countries of the world.

It is said that one day, when he was first rising to power, he was giving advice to his sons, and by way of example he took an arrow from his quiver and gave it to them, saying, “Break it!” It broke with only a little force. Then he gave them two arrows. They too broke easily. In this manner he kept adding arrows until there were ten, which even the strongmen and champions of the army were unable to break. “You are like these,” he said. “So long as you support each other, no one can achieve victory over you, and you will enjoy kingship for a long time.” Had the rulers of Islam followed this path, their dynasties would not have been extinguished.

As quoted in Rashid al-Din's Compendium of Chronicles (Jami' al-Tawarikh), Tome 1, Part 2, Chapter 2, Section 9, translated by WM Thackston, 2nd edition (2012). Classical Writings of the Medieval Islamic World: Persian Histories of the Mongol Dynasties, Vol 3. London: I.B. Tauris. Pg 403.