> The problem is that until a few hundred years ago, you could stand your ground and either win or lose (happened a lot) or you sought uninhabited land elsewhere )or a weaker party to kick out) That also happened a lot. Back then borders were defined by what you could actively defend, though treaties also existed.
That is the same situation that exists today. Might makes right is the only rule of nature. Treaties are just hopes that someone will help with defending your borders.
See Russia expanding its borders into what was previously recognized as Ukraine.
