Great Britain was challenged by other powers, primarily the German Empire and the Third Reich, during the 20th century. A century earlier it vied with Napoleonic France for global pre-eminence, and Hanoverian Britain's natural allies were the kingdoms and principalities of northern Germany. By the middle of the 19th century, Britain and France were allies in preventing Russia's appropriation of the Ottoman Empire, although the fear of French invasion led shortly afterwards to the creation of the Volunteer Force. By the first decade of the 20th century, the United Kingdom was allied with France (by the Entente Cordiale) and Russia (which had a secret agreement with France for mutual support in a war against the Prussian-led German Empire and the Austro-Hungarian Empire).