I've found what I've been doing in FOTS a lot more of is getting on a boat. Since the AI is more navy focused, I have been as well. As a result, I've got a pretty robust navy cruising around, and at the point where I inevitably get bottled in fairly early on by allies, I just continue building my economy, steadily crank out a couple stacks, put'em on a boat, and conduct a rear guard invasion of the opposing side. And I make a point of invading whoever is the strongest, or I suspect going to become the strongest clan among the opposition. Works like a charm.