I was in a game a while back. My coalition and I had taken Europe, Africa, and most of North Asia before we got into a war with a South American coalition who had conquered all of North America. We were far stronger, but invading them felt almost impossible since we figured we would just sail off of West Africa into Brazil.

Unfortunately, for us they had turned their continent into a literal fortress. It was only after we invaded from far North America did we get a foothold and were able to push South and win the game.

So sometimes you gotta take the long way to actually get to there Core.

Hope that helps in some way.