Here's a proposal, I'm not sure if it is good: Auto-loot.
It makes sense that the soldiers don't like marching around for no reason. In the middle-ages, it was very common for soldiers to pillage all lands around them. Glory and Victory could keep them, but otherwise it was common that no region would want to house moving soldiers, ever.
TMP could mean that when when a realm has been at peace for too long, troops get a random probability to auto-loot whatever region you are in. If you are in your own lands, your regions get damaged. If you leave your lands.... explain that to your neighbors. Or disband your unit, if you accept the price of an undefended land.
This would force war, without actually destroying the ability to wage war.
Hey, that is not half-bad.
Let's see what the rest think.
