Ignore the low star of people who clearly jumped in the film and didn't watch or read the subtitles.
I'll sum it up simply.
North and South are fighting each other to overcome the other and unify the land under one ruler.
In the film the North have infiltrated the South via the King's advisor. The South is made up of the central kingdom named phoenix city surrounded by different clans loyal to the king.
There was also a private army loyal to the king called the Chu Army.
So this advisor needs to destroy the clans loyal to the King before removing the King otherwise a new heir will take the spot.
So a tournament is held where each clan sends three fighters and by not attending the clan will commit a crime which will have them wiped out.
The winner of the tournament will get to lead the next assault on the north.
The undercover Northern advisor plans to have each clan fail and this bring shame and disbandment to each clan.
This does not go to plan due to events in the film which leads to a rushed plan poorly executed by the king advisor.
There is a plot here and a good one at that, but you really need to understand the basics of the above to put context to it all.