We have hot summers and cold winters because of the tilt of the Earth's axis. The tilt of the Earth means the Earth will lean towards the Sun (Summer) or lean away from the Sun (Winter) 6 months later. In between these, Spring and Autumn will occur.
Seasons are largely due to factors surrounding the Earth's tilted axis as it revolves ... The farther north you go, the bigger the differences in the seasons. ... Places near the Equator experience little seasonal.
Prior to the existence of the nation-state, Europe was comprised of several multi ethnic empires, the largest and most powerful of which was the Holy Roman Empire. Territory changed hands often. Many times, this took place because of marriage or as a result of war.