Tensions over rising Polish nationalism and the economic effects of the Continental System led to renewed confrontation with Russia. To enforce his blockade, Napoleon launched an invasion of Russia in the summer of 1812. The resulting campaign witnessed the catastrophic collapse of the Grand Army, forcing the French to retreat, as well as leading to the widespread destruction of Russian lands and cities. In 1813, Prussia and Austria joined Russian forces in a Sixth Coalition against France. A chaotic military campaign in Central Europe eventually culminated in a large Allied army defeating Napoleon at the Battle of Leipzig in October. The next year, the Allies invaded France and captured Paris, forcing Napoleon to abdicate in April 1814. He was exiled to the island of Elba. The Bourbons were restored to power and the French lost most of the territories that they had conquered since the Revolution. However, Napoleon escaped from Elba in February 1815 and took control of the government once again. The Allies responded by forming a Seventh Coalition, which ultimately defeated Napoleon at the Battle of Waterloo in June. The Royal Navy then thwarted his planned escape to the United States in July, so he surrendered to the British after running out of other options. The British exiled him to the remote island of Saint Helena in the South Atlantic. His death in 1821 at the age of 51 was received with shock and grief throughout Europe. In 1840, a million people witnessed his remains returning to Paris, where they still reside at Les Invalides.