Which as was posted before is half the problem. People need to get over the fear of losing. Perhaps the whole combat mechanics need to be changed so that there is some fun in losing?
I don't think it's just fear of losing. In several cases, it's mostly due to the lack of advantages. And I am not speaking here about noble-based advantages because that's not the point. I am just saying that once a realm wins and reduces his neighbors to tiny puppet, there will be stagnation. The large realm will have little point to pursue in further war activities: it's already large and it's already powerful. What's the point of pushing it further? Yes, the small realms should plan revenge and somehow try to actively plan for a future war and things like these, but their chances of success are so slim that no one does that and contents itself with sitting down.
all in all the main reason is that players lack the will (and perhaps the incentive) to change things, or that is my impression. Normally one would think that the strive for power will fuel enough conflicts - internal when external is not an option - yet if you take your time to think about it you'll see that very few dukes would gain that much from seceding and drawing a very likely war upon themselves. The same holds for rebellions. Very few lords would gain from changing allegiance and messing things up. In short: messing things up is almost never useful, the status quo is most of the times the best situation one can reasonably hope to find.
At least that is my experience. Quite often I found myself saying "ok things are getting boring, what can we do to stir them up?" and I have then realised that unless I deliberately do something wrong and possibly stupid, things will never shake up. The most likely answer one would get when asked "ok but why is there not an intra-SA conflict?" or "why is not one of the dukes of sirion seceding since it's so big" or "why is not SA trying to destroy the remaining non-theocratic realm bordering it" is again and again "why would we? what's the point in that?". And so playing reasonably and making your characters behaving rationally and not wildly very often leads to stagnation and boredom.
Unfortunately, I can't think easily of a solution for this. In general players should be more daring, but that's not happening not only because of "the fear of losing" but much more from the little they can gain from it. It's simply much more rewarding (in terms of promotions and ultimately gold gained) to play a noble to be good and loyal than wild and greedy.
