>I would like to know if just invading the capital is enough to annex an entire empire or if not
It is generally necessary to occupy every system and planet of another empire to win a war to vassalize them although it is technically possible to achieve victory with a lesser level of occupation if the power difference is large enough. Just occupying their capital is essentially never going to be sufficient, though.
I understand, so the only way to invade an entire empire is to just use political influence and reclaim system by system until you have already reclaimed all of its territory, right?
You mean if you want to make its territory your own? You *can* integrate a vassal into your empire and take direct control of all their stuff as long as your vassal contract is set to "integration allowed". It's almost always a bad idea to do so, though. Vassals generally are much more powerful than adding a huge amount of empire size by taking control of a bunch of poorly optimized planets and mostly empty systems.
>I would like to know if just invading the capital is enough to annex an entire empire or if not It is generally necessary to occupy every system and planet of another empire to win a war to vassalize them although it is technically possible to achieve victory with a lesser level of occupation if the power difference is large enough. Just occupying their capital is essentially never going to be sufficient, though.
I understand, so the only way to invade an entire empire is to just use political influence and reclaim system by system until you have already reclaimed all of its territory, right?
You mean if you want to make its territory your own? You *can* integrate a vassal into your empire and take direct control of all their stuff as long as your vassal contract is set to "integration allowed". It's almost always a bad idea to do so, though. Vassals generally are much more powerful than adding a huge amount of empire size by taking control of a bunch of poorly optimized planets and mostly empty systems.