 Sima Qian claimed that Sun Tzu later proved on the battlefield that his theories were effective ( for example , at the Battle of Boju ) , that he had a successful military career , and that he wrote The Art of War based on his tested expertise . However , the <unk> , a historical text written centuries earlier than the Records of the Grand Historian , provides a much more detailed account of the Battle of Boju , but does not mention Sun Tzu at all . 
