The Battle of Karakorum was the final battle in the Russian-Mongol war. The Russians, having defeated the Mongols at the Steppes, chased them back into Mongolia, where Genghis Khan gathered all his army together for one last stand. Russia had different ideas though; siege.
The Mongolian army had never been sieged, and at first thought it was Russian cowardice that they did not attack first. But as the months dragged on, disease broke out among the defending Mongols, and Genghis was forced to make his worst decision ever; surrender.
2/3 of the Mongolian army went with Genghis for honorable surrender. The remaining 1/3 prepared to attack.
5 days after the surrender, the remaining 1/3 charged out of Karakorum in a great ride. The surprised Russians were hurled back 2 miles before rallying and fighting them off. The entire 1/3 died.
Russia, now receiving the Mongolian lands of China, Central Asia, Persia, Northern India, and Southeast Asia is the dominant super power and a super state, but was conquered by Barbarossa in a later date.