Ally with not a soul, if only to make the game more interesting and realistic. It's such a crutch to declare war and then dupe the rest of the world into joining along with you. In RL, these "allies" would be fearing for their lives, knowing that their hides will be next.
A realistic game would have already brought most of the world against us. But since the game doesn't think for itself along those lines, shouldn't we help it out a bit? Or do we all need to finish this game STAT so we can get somewhere else?