It strikes me this issue was resolved by Alexander the Great in his conquests of City States. He wandered around with a great army, leaving a trail of vassal cities in his wake.
Simply arrive, gain control of System space and set an acceptable level of tithes for this system to be considered a valued part of your Empire.
If a system chooses not pay, now or later, then. Simply arrive, gain control of System space, restate your requirements then decapitate the leadership if they continue to refuse. Let the citizens choose new leadership, rinse and repeat.
Invasions are messy affairs that serve only to harm the very military resource you need to keep your loyal systems in line. Don't waste resources on invasions, let locals rule locals, so long as they pay your tithes. Only ever target the direct causes of tithes not being paid, the leadership and the tangible follies they produces (palaces, etc). Don't negotiate with leadership, exterminate. Its far cheaper. If they survive and start paying tithes again, great, it is a win-win.
Just my 2 cents. In an Interstellar Empire a single system is useful for one of only two things. Paying tithes or being an example of not paying tithes. Making it complicated just confuses your loyal subjects.
Simply arrive, gain control of System space and set an acceptable level of tithes for this system to be considered a valued part of your Empire.
If a system chooses not pay, now or later, then. Simply arrive, gain control of System space, restate your requirements then decapitate the leadership if they continue to refuse. Let the citizens choose new leadership, rinse and repeat.
Invasions are messy affairs that serve only to harm the very military resource you need to keep your loyal systems in line. Don't waste resources on invasions, let locals rule locals, so long as they pay your tithes. Only ever target the direct causes of tithes not being paid, the leadership and the tangible follies they produces (palaces, etc). Don't negotiate with leadership, exterminate. Its far cheaper. If they survive and start paying tithes again, great, it is a win-win.
Just my 2 cents. In an Interstellar Empire a single system is useful for one of only two things. Paying tithes or being an example of not paying tithes. Making it complicated just confuses your loyal subjects.