Okay, let's get this out of the way. In a region, the nation with the most endorsements is automatically appointed Delegate. This usually grants significant powers, including the ability to eject other nations from the region.
One way this can work is a region's residents endorse the nation they think would make the best Delegate, and that nation rules over it with a wise and gentle hand. Another way is that nations make private deals on who to endorse in order to make sure that their ally gets into power. A third way is a bunch of nations from a different region unexpectedly move in, endorse each other, and seize the Delegacy in a coup. This one is called "the invasion game" (also "raiding," or "R/D" for raiding/defending).
The invasion game is somewhat controversial: some people find it fun to crash into other people's regions, some people enjoy trying to stop them, and some think the entire practice should be banned.
Both the invader and defender sides are highly organized, although there are plenty of smaller-scale conflicts.
Detailed information can be found in this forum post: "Basics of Military Gameplay."
interessant