It was called by Cao Cao and led by Yuan Shao , and many powerful warriors joined it . After Dong Zhuo 's death through the hands of his foster son LÃ 1\/4 Bu , Emperor Xian was controlled by Dong 's associates . LÃ 1\/4 Bu , Dong 's foster son , left the room for the stable to select a better horse for Cao , who complained about his slow ride .