This idea that politics or partisanship is something new to the modern world is fascinating.

I see it constantly among people that have little exposure to actual historical documents.

I suspect its origin is a bit of nostalgia for the "simpler times" of the past and the often horrendously bad methods many people learn history.

Often history is presented as a cleaned up and certain narrative - At simplest, a history of events that happen on dates. They often leave out the machinations, plotting, betrayals, and intrigue that was almost always present.

We strip the messy humanity from history as we build simplistic narratives.

Looking back it may seem to be obvious that Nazis should not have been appeased, but at the time there were many intelligent and informed people who thought otherwise. Same with the US getting involved in the War.

Politics have been a thing as far back as we have written records.