Complex sentence: After Jebe scored victories over Kuchlug of Kara-Khitan, Genghis Khan, though glad of his general's victory, was said to be concerned, not knowing if Jebe would seek greater ambition at his expense and rebel against him.
Split into simpler sentences: After Jebe scored victories over Kuchlug of Kara-Khitan, Genghis Khan was said to be concerned. Although Genghis Khan was glad of his general's victory, he was unsure if Jebe would seek greater ambition and rebel against him.