 Thus, he, Prince Ping Yuan and Mao Sui licked the blood of animal (usually chicken) and swore (This was a tradition of oath in ancient China, the idea was that putting blood on the mouth solemnified the words of the treaty of alliance, and signified the punishment that would come on whoever broke the agreement) Three months later, the allied forces of Zhao and the Chu defeated Qin's army and saved Han Dan.After Prince Ping Yuan returned to Zhao, he treated Mao Sui as the most honorable guest.He said with a deep sigh