Before revision: This was successful through most of the 19th century, until the First World War collapsed the post-Napoleonic system amid increasingly acute nationalist tensions, which led to the formation of Germany and the collapse of the Austrian, Russian, and Ottoman empires.
After revision: This was successful through most of the 19th century, until World War I collapsed the post-Napoleonic system amid increasingly acute nationalist tensions, which led to the formation of Germany and the collapse of the Austrian, Russian, and Ottoman empires.