Sun Tzu was not a king or a member of any of the principal families of nobles. He earned his reputation as a mercenary warlord after a friend recommended him to the court of the King of Wu. As legend has it, the King asked Master Sun if he could train anyone, even concubines. Master Sun said he could; when the women refused to obey his commands he had their leaders beheaded. After that, all of them performed flawlessly.
When you say "I can't", is it a result of not knowing or not willing?