The oath of death (1971)

Three Sung loyalists decide to become blood brothers to fight the tyranny of the Tartar invaders. They build a stronghold and christen it 'The Flying Dragon Fortress' up in the hills. Gathering together a devoted army of followers, the three brothers wage war against the Tartar defense. Desiring to oust the oppressors altogether, Ma Ching plans to coerce an ally, Hong Zhang Chung to release the kidnapped Tartar princess in what initially seems a strategic and civil effort to gain points with the court. Not long after, it soon becomes apparent Ma desires both a great position and power and is willing to sacrifice anything and anyone to get it.