Actually, allowing a fellow Lord's state to fall to ruin is a sound strategy. I know everyone's got this "the nobles are just dumb dumbs for giving their enemies an advantage for no reason other than just pride and being snotty nobles" but there's actually more nuance.
Their foreign enemy is-and remember this clearly-human. They aren't Orks, Demons, or any abhuman abomination that cannot be reasoned or dettered. They're just humans, they can scared, bribed, and killed when it comes down to it. Hell, these Nobles are likely in dealings with the enemies and would have it sweet if they were
forced to hand over the nation. Like "Oh no, my king-who I would never betray-the enemy is demanding our subservience. I guess you, my-totally irreplaceable-lord will just be behead by them because there is no other option. I'll stay here to watch over our people as their ruler-I mean, overseer-I mean middle man with the new King-Usurper sense it is actually very reliable to use the already in place aristocracy to govern newly conquered nations so long as they continue to pay tribute.
Like, seriously, this stuff happened and still happens alot. And it actually works if you play your cards right.
@Eridian
These Nobles are Feudal Lords with their own individual Armies. There really isn't ONE centralized army, unless the King calls the Nobles from several regions to fight in a war. So when one of their peers suffer, they are exempt to the suffering and can benefit from being able to devour their competition.
