Alrighty so, Ive searched for info on these and cant find it, at least not by the search terms Im using.

At the start of a Date campaign on Normal, I fought three battles in quick succession against the neighbor in Udo. After one of them, in the mountain gap between our two provinces, a little stellae/pillar model appeared next to the road near my army. Hovering over it with my mouse cursor displayed a box saying "Battle of ____, 1540."
I'm assuming it was a monument to the battle. But how the heck did I get it? I have not seen a single one yet in my Shimazu campaign on hard.

My first though was I'd accidentally clicked 'record game' and it was a symbol of a battle recorded there. But I havent tried again to test it.

Second idea was that it's the site of a historical battle that I ended up fighting 'in spirit' totally by accident.

Anybody know what that was and how to get it again?