A common language may have been seen to serve as the basis of a nation, but as contemporary historians of 19th-century Germany noted, it took more than linguistic similarity to unify these several hundred polities. The experience of German-speaking Central Europe during the years of French hegemony contributed to a sense of common cause to remove the French invaders and reassert control over their own lands. The exigencies of Napoleon's campaigns in Poland (1806–07), the Iberian Peninsula, western Germany, and his disastrous invasion of Russia in 1812 disillusioned many Germans, princes and peasants alike. Napoleon's Continental System nearly ruined the Central European economy. The invasion of Russia included nearly 125,000 troops from German lands, and the loss of that army encouraged many Germans, both high- and low-born, to envision a Central Europe free of Napoleon's influence. The creation of student militias such as the Lützow Free Corps exemplified this tendency.