I've been studying European medieval history for a year or so now, and you're right---that shit was absolutely normal. I'd say it was how humanity operated from the first formation of the first two tribes until the end of WWII.

The massive slaughter of the World War period seems to have ended most nations' willingness to take land at the point of a sword ... but Putin's invasion of sovereign Ukraine is not a good sign for that postwar change becoming permanent.