Conversation so far:
When did Julius Caesar begin the military campaign?
58 BC
Where did Julius Caesar start the campaign in 58 BC?
The Gallic War mainly took place in what is now France
Was the military campaign in the Gallic war where it is now France successful?
it was Roman victory resulted in the expansion of the Roman Republic over the whole of Gaul

Question: What did he do once he won?
Self-contained rewrite: What did Julius Caesar do once he won and the Roman Victory resulted in the expasion of the Roman Republic over the whole of Gaul?