Why Britain Risked Everything to Stop Napoleon’s Empire

Britain's war to stop Napoleon was a desperate gamble against total domination. Facing invasion and economic ruin, their strategy became one of survival.

Updated: May 2, 2026 written by Mike Cohen,BA History

storming of bastille painting 1789
The Storming of the Bastille, 14 July 1789.

 

Few conflicts in history have cost one country as much as the Napoleonic wars cost Britain. The fighting spanned from 1803 to 1815, with a major break for peace from 1802 to 1803. The total cost of the war came to about £1.65 billion, equivalent to £190 billion in today’s currency adjusted for inflation. Most of that money was covered by government borrowing. The rest came largely from taxes, including a new income tax introduced in 1799. Yet the real question of why Britain kept paying this price year after year is one that historians still debate today.

 

The Killing of King Louis XVI Made War Inevitable

Vintage Illustration of The Conquerors of the Bastille, based on the painting by Francois Flameng
Vintage Illustration of The Conquerors of the Bastille, based on the painting by Francois Flameng. Source: iStock/Getty.

 

Britain largely chose to stay out of European affairs after the French Revolution broke out in 1789, but the situation soon spun out of control, compelling London to get involved. Complications began in late 1792 when French troops moved into Belgian territory. This put pressure on Dutch trade routes and on British maritime commerce along the River Scheldt. France soon declared war on both Britain and the Netherlands on 1 February 1793. At the time, the killing of King Louis XVI on 21 January 1793 had already drawn a line between the nations, as it made the new government appear more hostile and illegitimate. On one side stood the conservative royalist United Kingdom and its allies and on the other, the radical Republican France. Hostilities increased further when Napoleon came to power.

 

Napoleon’s Broken Promises Forced Britain Back to War

David Emperor Napoleon Study Tuileries
The Emperor Napoleon in His Study at the Tuileries, 1812.

 

A brief period of peace from 1802 to 1803 ended when Britain declared war on France on 18 May, 1803, bringing the Treaty of Amiens to a close. Britain had refused to evacuate Malta as required by the treaty, a main sticking point. Bonaparte on his part, also violated other provisions by making himself President of the Italian Republic (formerly the Cisalpine Republic) in early 1802 and by failing to fully withdraw French troops from the Batavian Republic (Holland) as stipulated. The threat of a French landing on British shores hung over the country for much of the period between 1793 and 1805. By then Britain had forged major alliances on the continent to keep France busy.

 

Napoleon Tried to Starve Britain Into Surrender by Waging Economic Warfare

La Paix d Amiens Jules Claude Ziegler
David Emperor Napoleon Study Tuileries

 

With no way across the Channel, Napoleon tried a different strategy. On 21 November, 1806, he issued the Berlin Decree, setting up the Continental System which banned all trade with Britain across French-controlled Europe. The territories included French-occupied areas and vassals such as Spain, and later Prussia after its defeat, parts of Northern Germany, and other large areas of Europe. On 17 December, 1807, the Milan Decree extended this to any neutral ship that had stopped at a British port. The plan was to flood British factories with unsold goods and drain gold from the British treasury until the government was forced to ask for peace. The plan did not work. British merchants found ways around the rules. With naval power on their side, they were well-placed to keep smuggling goods into Europe. Britain was determined to win.

 

Britain Did Not Want to Lose Portugal as a Trading Ally

Tratado de Amiens Fragata Mercedes exposición
Page of the Treaty of Amiens with the eight seals and the eight signatures of the signatories.

 

Because Portugal refused to stop trading with Britain, the French army marched through Spain and took Lisbon in November 1807. Napoleon even went a step further and removed the Spanish royal family from the throne, putting his brother Joseph on it as King of Spain in 1808. The Spanish people strongly opposed this, and soon, a nationwide uprising followed. Spain quickly became a serious problem for Napoleon. At the Battle of Bailén that occurred in July 1808, the Spanish army trapped and forced the surrender of about 17,000 French troops in what was the first major surrender of a Napoleonic army on a European battlefield. By then, Spain had already asked Britain for help, and in August 1808 Lieutenant-General Arthur Wellesley landed with 15,000 troops at Mondego Bay in Portugal. He and his men fought across Portugal and Spain for nearly six years before finally pushing the French armies back and helping defeat them on French soil.

 

Britain Deemed Napoleon a Threat to Its National Security

arthur wellesley hoppner
Lieutenant Colonel Arthur Wellesley, aged 26, in the 33rd Regiment, by John Hoppner, 1795. Source: Wikimedia Commons

 

Following British campaigns, Napoleon abdicated the throne in April 1814 and was sent to the island of Elba. At the time, Britain deemed him a threat to its national security and was resolute in keeping him away from the throne. He, however, returned to France in March 1815 and raised a new army, but was defeated at the Battle of Waterloo on 18 June 1815 by a British-led coalition under Wellington and the Prussian force under Field Marshal Gebhard Leberecht von Blücher. The battle ended over two decades of near-constant war, after which the winning countries once again restored the French monarchy, placing King Louis XVIII on the throne.

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Mike CohenBA History

Mike is Bachelor of Arts History graduate from the University of Leeds. As a historian, he loves to write about historical figures and events, especially those that continue to influence the modern world.