rebellions in Italy which, although suppressed, foreshadowed future nationalist and anti-French risings. After Schönbrunn, Austria became a French ally and this was cemented by the marriage of Napoleon to the Austrian princess Marie Louise. Background In 1809, Europe was embroiled in warfare, pitting revolutionary France against a series of coalitions in the Coalition Wars almost continuously since 1792. A brief period of peace followed the March 1802 Treaty of Amiens before British-French relations deteriorated, leading to the War of the Third Coalition in May 1803. Britain was joined in their coalition by Sweden in 1804 and Russia and Austria in 1805. In August 1805, the 200,000-strong French Grande Armée invaded the German states, hoping to defeat Austria before Russian forces could intervene. The French emperor Napoleon successfully wheeled his army into the Austrian rear and defeated them at the Battle of Ulm, fought from 15 to 20 October. The Austrian capital, Vienna, was captured in November and a Russo-Austrian army was decisively defeated at the 2 December Battle of Austerlitz. The Treaty of Pressburg, signed soon afterwards, ended Austrian participation in the war. Austerlitz incited a major shift in the European balance of power. Prussia felt threatened in the region and, alongside Russia, declared war against France in the 1806 War of the Fourth Coalition. After French victories at the Battle of Jena and the Battle of Auerstadt on 14 October, France occupied the Prussian capital, Berlin. France invaded Poland in November, where Russian forces were stationed, and occupied Warsaw. Russian and French armies fought in February 1807 at the violent, indecisive Battle of Eylau. The action in Poland culminated on 14 June 1807 when the French defeated Russia at the Battle of Friedland. The resulting Treaty of Tilsit in July left France as the dominant power in Western Europe, with many client states including the Duchy of Warsaw. This weakened Prussia and allowed Russia to expand into Finland and South-Eastern Europe. Peninsular War In 1807 France tried to force Portugal to join the Continental System, a commercial embargo against Britain. When the Portuguese Prince Regent, John refused to join, Napoleon sent General Junot to invade Portugal in 1807, resulting in the six year Peninsular War. The war weakened the French Empire's military, particularly after Spanish forces and civilians rebelled against France after Napoleon overthrew the Spanish king. After the French defeat at the Battle of Bailén, Napoleon took command