After uncovering a conspiracy plotted by the king a Templar is forced to intervene in the king’s plot before it leads to civil war.

The latest draft is an improvement but it still lacks detail.

What will the knight actually do in order to achieve his goal?

His actions are going to be most of act 2 i.e most of the film and therefore they need to be specified in the logline. Will he fight other knights? Or investigate suspicious activity in the royal court? Or seek out spies? etc? What ever he does it needs to be specified.

Hello, your last version is not bad, but I strongly recommend?to define exaclty what you mean by "intervene". Your movie hides behind this word.

War against who?

The premise is inevitably going to be compared to "Kingdom of Heaven". ? Hasn't Ridley Scott already been there, done that? ? A corrupt king intent on breaking a fragile peace, provoking war against Saladin is one of the film's story threads.

Problem is, the king of jerusalem is the one who will be causing the war.

The logline has evolved well over the course of this thread.

I think it is now clear that the inciting incident is the discovery of the plot, perhaps then place it at the start of the logline instead of at the end?
E.g:
After he discovers a plot, a templar knight must uncover a traitor in the king of Jerusalem's ranks to prevent the outbreak of war.

I added in that he needs to find a traitor to specify how he will prevent the war.

'Maintain peace' and 'save from war' seem the same.

A Templar knight struggles save J from war by (specific action) thwarting a conspiracy ?by the corrupt king.

Gives you a little more room for story.