In 1199 the two allies marched to attack the Naimans, a people strong and famous while under Buga Khan, an able ruler, but when this Khan died his two sons, to gain a certain concubine left by their father, began a murderous quarrel, which brought about the division of the country. The elder man, Baibuga, called Taiyang, [5] by his subjects and his neighbors, retained the level country, while Buiruk, his brother, took mountain places. Each ruled alone, and each was an enemy of the other. Wang Khan and Temudjin, remembering former robberies by the Naimans, and wishing too to add wealth and power to what they themselves had, attacked Buiruk at Kizil Bash near the Altai. They seized many captives and much precious booty. Buiruk then moved westward followed closely by the allies and fighting with great vigor. One of his leaders, Edetukluk, who brought up the rear guard, fought till his men were all slain, or made prisoners. He struggled alone then till his saddle girth burst, and he was captured. After this the allies came in contact with Gugsu Seirak, another of the Naiman commanders, who had much greater forces and had chosen his position. This man had plundered Wang Khan’s brother somewhat earlier and a portion of his kinsfolk. The allies had met him already, and hoped now to crush him. They would have attacked him immediately, but since evening was near they chose to wait till next morning for battle. Jamuka, ever ready to injure Temudjin, went to Wang Khan and made him believe that he was on the eve of betrayal, and would be ruined by Temudjin and the Naimans. Wang Khan set out for home that night. Temudjin thus deserted was forced to withdraw which he did unobserved. Gugsu Seirak followed Wang Khan in hot haste and overtook his two brothers. He captured their families, as well as their property and cattle. Then he entered Wang Khan’s land and found there rich booty of all kinds. Wang Khan sent Sengun, his son, to meet Seirak; meanwhile he hurried off messengers to Temudjin, and begged of him assistance. Temudjin considering the plight of his ally, but still more his own peril should Wang Khan’s men be routed and captured by the Naimans, sent his four ablest chiefs to assist him. These were Boörchu, Mukuli, Boroul and Jilaun. These four led their men by hurried marches, and had just reached the battle-ground when Wang Khan’s force was broken, his best leaders killed and Sengun, his son, on a lame wounded stallion, was fleeing. All the Khan’s property had been taken by the Naimans. Boörchu dashed up with all speed to Sengun, gave him the horse on which he himself had ridden up to that moment and sat then on the gray steed which Temudjin had given him as a mark of great favor. He was not to strike this horse for any reason; he had merely to rub the whip along his mane to make him rush with lightning speed during action.