Europe prides itself with its multi-thousand year history. They laugh at Americans when we say our neighborhood is old at 100 years, they have special rocks that can reliably be traced back a few thousand years. However, they hate each other.
As the above video can show in 3 minutes what no high school history class could ever get across. The many border changes and invasions of countries by other countries of Europe over the last 1,000 years. You just can’t get those drastic border changes without hating your neighbors, and wanting to invade them.
It’s much easier to get a sense of how big the various Empires are by watching them expand across borders, and then contract. You just can’t get that by reading a book.