The Napoleonic Wars (1803–1815), were a series of major conflicts pitting the French Empire and its allies, led by Napoleon I, against a fluctuating array of European powers formed into various coalitions, financed and usually led by Great Britain. The wars stemmed from the unresolved disputes associated with the French Revolution and its resultant conflict. The wars are often categorised into five conflicts, each termed after the coalition that fought Napoleon; the Third Coalition (1805), the Fourth (1806–7), Fifth (1809), Sixth (1813), and the Seventh and final (1815). 

Napoleon, upon ascending to First Consul of France in 1799, had inherited a chaotic republic; he subsequently created a state with stable finances, a strong bureaucracy, and a well-trained army. In 1805, Austria and Russia waged war against France. In response, Napoleon defeated the allied Russo-Austrian army at Austerlitz in December 1805, which is considered his greatest victory. At sea, the British inflicted a severe defeat in October 1805 upon the joint Franco-Spanish navy, securing British control of the seas and preventing the invasion of Britain itself. Prussian concerns about increasing French power led to a resumption of war in October 1806. Napoleon quickly defeated the Prussians, and defeated Russia in June 1807, bringing an uneasy peace to the continent. The peace failed; war broke out two years later in 1809, and this coalition was soon defeated.
Was Britain invaded?
the British inflicted a severe defeat in October 1805 upon the joint Franco-Spanish navy, securing British control of the seas and preventing the invasion of Britain itself.