The country's king is an arrogant, prideful fool
I am looking at the first king side chapter, and that might be a "bit" of an understatement...
I mean signing a peace treaty after fighting to a stand still only to get rid of your greatest assest then declare war again on the nation you just signed a treaty with, who is at the same strength as they were, is beyound idiotic. It is insanity.
I can inderstand if after taking the time to recover your nation and forces you feel you recovered faster and to a greater degree (which would likely still be reckless), or some disaster affected that nation, but after crippling yourself it is just asking for your lands to ve conquered. Plus no one will ever trus your word again, so you effectively end up hostile to every neighbouring country as they are all worried you will go after them next.