The achievements

capturing the capitol does not stop the soldiers and politicains from moving to a new base

the soldiers refuse to surrender

it's like this:

lets say people have taken over the living room of your house and are moving across the main level of your house.

what are you going to do?

naturally, you would move to the upstairs and not just let these people take over you.

this is what capitals is like. once you capital is taken over, that moves them to a different region.

and just because the capital fell doesn't mean the battle is won. even though the general is dead, the soldiers fight on. you still have more land to take over even with the capital gone.