[PvK]

Sounds like you've won but with no fanfare. I often tend to declare myself victorious, and/or keep the save games as fun/interesting references that I go back and look at from time to time, and sometimes play another turn (or a few).

If you want the official program-endorsed victory before world domination, you can set victory conditions.

One can also decide that one's empire has become too large to micro-manage, and finish the game by being sloppy with most of it, retiring the elite veterans to home guard, partying, feasting, and glorious opportunities, and doing the mopping up with clumsy mass armies. If one can resist the compulsion to micro-manage, and roleplay the mopping up, it can either lead to a fairly quick official win, or let the enemy build up a more interesting challenge by giving them some breathing room.

PvK