Go into the house you own, start throwing their crap out, when they attack, defend yourself against the thieves with normal force you would use stains someone in your house. If anyone tries to prosecute you, the fraudulent documents will prove they are criminals and never tenants.
I remember reading a story earlier this year about a guy that did just about that although instead of a confrontation he staked out the property and waited. When the squatters left he broke in (isn’t that a shame having to break in to your own property) and threw their crap out and changed the locks, all before they returned.
So essentially what he did was what they did to him in reverse.
Brilliant but a real shame he had to go through all that just to regain control of his own rightfully property.