Modernism really started with people getting infatuated with the idea of "it's the twentieth century, is this suitable for the twentieth century." This happened before the First World War and it wasn't just the soldiers. You can see it happening if you read the Bloomsbury biographies. It was a reaction to a great extent against Victorianism. There was so much that was repressive and stuffy. Victorian buildings were associated with it, and they were regarded as very ugly. Even when they weren't ugly, people made them ugly. They were painted hideously.