On the second and last day of the Battle of Aspern-Essling (near Vienna, Austria), Napoleon I is defeated in a major battle for the first time in his career, and repelled by an enemy army for the first time in a decade.

In the Battle of Aspern-Essling, Napoleon crossed the Danube near Vienna, but the French and their allies were attacked and forced back across the river by the Austrians under Archduke Charles. It was the first time Napoleon had been personally defeated in a major battle, as well as his first battle defeat in 10 years since the Siege of Acre, and his first battle defeat as head of state, although he did suffer a tactical defeat in the Battle of Caldiero (1796). Archduke Charles drove out the French but fell short of destroying their army. The French lost over 20,000 men including one of Napoleon's ablest field commanders and closest friends, Marshal Jean Lannes.

Vienna is the capital, most populous city, and one of nine states of Austria. It is Austria's primate city, with just over two million inhabitants. Its larger metropolitan area has a population of nearly 2.9 million, representing nearly one-third of the country's population. Vienna is the cultural, economic, and political center of the country, the fifth-largest city by population in the European Union, and the most populous of the cities on the river Danube.

Napoleon Bonaparte, later known by his regnal name Napoleon I, was a French general and statesman who rose to prominence during the French Revolution and led a series of military campaigns across Europe during the French Revolutionary and Napoleonic Wars from 1796 to 1815. He led the French Republic as First Consul from 1799 to 1804, then ruled the French Empire as Emperor of the French from 1804 to 1814, and briefly again in 1815. He was King of Italy from 1805 to 1814 and Protector of the Confederation of the Rhine from 1806 to 1813.