There's the problem. You would claim that a given area of land, which you aren't actively using
Who said he's not using it? Say he's a farmer and he just planted his fields. Is he no longer "using" that land and that equipment? Does it matter if he is "using" it or the people who agreed to work on his behalf? What if he builds or purchases robots to work on his behalf?
a party, meaning no offense to you, starts using it because they do not recognize vacant or unused property
Are you saying that the syndicalists do not
understand the concept of private property, not just disagree with it? They don't realize that by using the equipment or land, they are depriving the person who
claims to own it of its use at a time of their discretion?
you will try to drive them away or destroy them thereby plying your trade--land ownership, if you could call it a trade--by violence.
The non aggression principle only justifies a proportional amount of force to be used in self defense.
Perhaps you will hire someone else to do it. What other recourse does a capitalist have? The two ideas aren't compatible.
Would the type of society you envision not have any sort of protection measures? How does this society respond when one or more individuals decide they can own private property? It starts off with a group of people building a machine that makes really useful widgets. Soon, everyone wants to use the machine to make their own really useful widgets, but the creators don't think it's fair that they put in all the work and everyone else reaps the rewards. So they start denying people use of the machine, first using words, and then physical force. Would all of society be obligated to prevent this violence, or would there be a specialized group of people that do so?