This is the basis for the GW world wide campaigns, the difference being that instead of winning territories, players effect the percentage hold their faction has on a region, planet, system, or sector.
Territorial campaigns work well with gaming clubs because they're don't restrict who plays who. You can either battle of territories that don't need to be adjacent to your own territory or simply work on the basis that the winner of a battle can claim one of the losers territories. This way, any player in the campaign can play any other player without needing to worry about their positions on the map.
It's fine to add special rules to cover specific territories or ongoing effects to spice the campaign up a little or just keep it simple as a way of tracking how well the players are doing over the course of the campaign.
When setting up a territorial campaign, it's best if each player has a few territories to start with. Ideally, this should be at least equal to the number of players plus one, so if there's 4 players, each player should start with 5 territories. This will make sure than even if everyone attacks one player in the first turn (which is very unfair), then they're not going to get wiped out of the campaign. Alternatively, you could say that players can never lose their capitals or starting territory, so that players who don't do so well in their battles aren't excluded from the campaign by losing all their territories.
Here's a map that could easily be used for either territorial or a true map campaign. Notice how they've included special locations that could have ongoing effects in the campaign.
Contributed by Tokkan (Freebootaz)
As you can see, territorial campaigns offer a simple way to a group of players to track their games over a period of time although they don't offer much in the way of strategical way. If you're looking to add a little strategy to your campaign, then consider a node based campaign.
Have I missed anything? have you got something add? add it in the comment below.