During the 30 years war, between Protestants and Catholics, something like 1/3 the population of Europe died -- either killed outright or starved to death.
Perhaps one-third of the population of Germany died during the Thirty Years’ War, but hardly one-third of all of Europe. Many countries were not directly affected and most if not all of the fighting was within the Holy Roman Empire. Of course the English had their own civil war during the same years, and there was some fighting in Ireland, but they aren’t seen as part of the Thirty Years’ War and I doubt the death toll was anywhere close to one-third in either country.