Imagawa campaign: "Short Letters to Mariko"

[caravel]

The problem with abandoning one side of a split domain is that you're then presented with - what is essentially - a "quasi Shimazu" campaign involving the same typically linear west to east sweep of the map. I prefer to try and hold both regions and then join them up. This makes for a much more interesting and less predictable campaign. It also means that you're less likely to be facing a massive horde on the other side of the map once you get there.

-Edit: Another interesting aspect to this is shipping troops from east to west, or vice versa, to reinforce your armies there.