>>55153562My headcanon is that way back in ye olden times, the top pokemon trainers (or whatever they would have called them at the time) were akin to bronze-aged warlords, commanding powerful pokemon and underlings with the own pokemon to wage the sort of barbaric wars over territory and resources that we saw with Rome, Carthage, Persia, the Mongols, etc.. But now that the pokemon league exists, the type of trainers who would become a warlord instead just become high-level competitive pokemon trainers, gym leaders, elite four members, champions, etc. Basically the league gives them structure to have their "wars" in a way that doesn't involve conquest and destruction.
Since the pokeworld seems to exist in a state of post-scarcity, and since the most powerful weapons available to society (the pokemon themselves) are stronger when used with the power of friendship, people have much less of a reason to go to war and can accomplish less by waging war. So war as we know it in our world doesn't really happen anymore.
I choose to ignore Lt. Surge because he, like a lot of the lore from Gen 1, is a weird outlier, and the rest of the setting makes more sense if you just cut out the part about him being an American soldier