Slitherine

I understand that they will establish a commandery in my lands and take money from every region they have one. And that I cannot remove these buildings. It is a valid mechanic.

It is also frustrating to see them establish these things in my richest regions and have their troops wander through my territory at will.In my latest game, they have established a nation that has many valuable regions, and they have a large number of units.

And when I got excommunicated, They joined the crusade against me and sent a huge army into my territory, but the pope lifted the excommunication in one turn, and the crusaders did not attack me. Nevertheless I see the threat.

I am thinking of declaring war on them, but I have no idea of whether this will enable me to destroy their buildings in my territory.

I know that the Hungarians expelled the Teutonic knights from their territory, and the French pretty much destroyed the Templar order. I am wondering if the game offers any means to accomplish the same result.

if you click on one of their units it should open the panel where you can access the diplomacy window. From there you should be able to declare war on them.
I've never gone to war with them myself, originally in beta they used to pillage your regions they were in, much better now. I have had them show up in my regions and then disappear with their buildings without any input from me. Maybe just keep an eye on them and see if they are really that much of a bother. Then if they really annoy you put them to the sword.

Thanks for the good advice. I think I will declare war on them. At least I can destroy their units and conquer their empire.

I wonder if that will get me excommunicated. I am willing to take the risk.

This is how you get rid of the Templars, or any military order who has built a commandery in your regions and taking your money and reducing your authority...

Go to war against them. Every one of the many commanderys in my lands were gone the turn after I declared war, and my income shot up. I also had some great battles with the templars, which were mostly successful, with one severe defeat. The Templars have some units of knights, just knights, and they are tough.

Anyway, great fun!

My war with the templars was a lot of fun, and it ended without my taking any territory from them.

But I did get rid of their commanderies. They are now sending small forces into some of my best regious, probably intending to build a new commandery. But I send a small force of my own into the same regions, and it seems to keep them from completing their own building.