The story of pre-unified China must be a popular one. Jet Li's Hero made the assassination of the King popular.
This is another story made a few years earlier. It stars the incredibly beautiful Li Gon (Memoirs of a Geisha, 2046, Miami Vice) as the King's lover, who was sent to recruit an assassin so that the King could defeat him. She recruits Fengyi Zhang, but falls in love with him.
No matter, he is not able to complete the mission anyway, as the King knew about him beforehand. I suspected he also knew, but went anyway.
It was a beautiful story with massive military operations, and, of course, another chance to see Li Gong.