This map shows how people across Europe would respond to that question.
The data is based on a survey from Gallup International, and uses a scale going from red to blue. A dark blue means that a more citizens of that country would be happy to take arms for their nation, whereas the red countries have more objectors.
Finland had the most people who said that they would (74%), followed by Turkey on 73% - notably both those countries currently have some form of national service.
The countries with the fewest people who said they would be willing to fight tend to be concentrated around the heartland of Europe, with Belgium on 19%, Germany on 18%, and the Netherlands with just 15% of the population saying they would.
Britain is also pretty low, with around a quarter saying they would fight.