Hoping to isolate and weaken Britain economically through his Continental System, Napoleon launched an invasion of Portugal, the only remaining British ally in continental Europe.

At first, the Austrians won a significant victory at Aspern-Essling, but were quickly defeated at Wagram.

The treaty failed to end the tension, and war broke out again in 1809, with the badly prepared Fifth Coalition, led by Austria. Napoleon soon defeated the Prussians at Jena-Auerstedt and the Russians at Friedland, bringing an uneasy peace to the continent. Concerned about increasing French power, Prussia led the creation of the Fourth Coalition with Russia, Saxony, and Sweden, which resumed war in October 1806. In December 1805, Napoleon defeated the allied Russo- Austrian army at Austerlitz, effectively ending the Third Coalition and forcing Austria to make peace. This victory secured British control of the seas and prevented a planned invasion of Britain. Frank McLynn argues that Britain went to war in 1803 out of a 'mixture of economic motives and national neuroses – an irrational anxiety about Napoleon's motives and intentions.' The British fleet under Admiral Nelson decisively crushed the joint Franco-Spanish navy in the Battle of Trafalgar in October 1805. War broke about soon after, with Britain declaring war on France on, ending the Peace of Amiens, and forming a coalition made up of itself, Sweden, Russia, Naples, and Sicily. He then organised a financially stable French state with a strong bureaucracy and a professional army. Upon realising the Coup of 18 Brumaire, whereby he became the First Consul of France in 1799, Napoleon assumed control of the politically chaotic French First Republic. There were seven Napoleonic Wars, five named after the coalitions that fought Napoleon, plus two named for their respective theatres: (i) the War of the Third Coalition (1803–1806), (ii) the War of the Fourth Coalition (1806–1807), (iii) the War of the Fifth Coalition (1809), (iv) the War of the Sixth Coalition (1813–1814), (v) the War of the Seventh Coalition (1815), (vi) the Peninsular War (1807–1814), and (vii) the French invasion of Russia (1812). The wars originated in political forces arising from the French Revolution (1789–1799) and from the French Revolutionary Wars (1792–1802) (the War of the First Coalition (1792–1797) and the War of the Second Coalition (1798–1802)), and produced a period of French domination over Continental Europe.

The Napoleonic Wars (1803–1815) were a series of conflicts fought between the First French Empire under Napoleon (1804–1815), and a fluctuating array of European coalitions.

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