After the outbreak of the French Revolution in 1789, Britain had remained neutral, watching from the side-lines, but in 1793, when French troops occupied Belgian lands, threatening the Dutch as well as British overland trade via the River Scheldt, war was instigated.  British troops were sent onto continental Europe, but were defeated at the battle of Hondschoote in the September of 1793. 

Britain at this time was allied to the major powers of Europe; the Netherlands, Spain, Austria Prussia and Piedmont-Sardinia.  Had they combined and struck at France it is more than probable that the French Revolution would have been put down and the French Bourbon Monarchy restored.  However, the allies failed to decide upon an organised strategy; The British concentrated their forces in overseas possessions, whilst squandering money to help finance her allies, who used the money for differing aims.  By 1796, only Austria and Britain remained united against France, with Austria receiving so much British financial support that the British economy began to strain.  A punitive French expedition in 1796 failed, and William Pitt the younger sued for peace with France. 

1797 saw the Bank of England suspend gold payments, Austria make peace with France, and the Netherlands and Spain join the French cause.  Luckily, a naval battle was fought against the Spanish fleet at Cape St. Vincent, helping to maintain British naval hegemony.  As Pitt again attempted peace negotiations, ultimately failing, this left Britain to fight France alone. 

Napoleon attempted an expedition to Egypt during 1797, and the British send a fleet to try and stifle his attempts at gaining dominance over an important trade area.  After defeating the French at the battle of the Aboukir Bay, and the victory helped persuade Austria and Russia to join Britain in a new coalition against the French.  In 1799 things changed when Napoleon took charge in France, directing his forces well and reconquering Italy, whilst winning the battle of Hohenlinden. 

A Peace treaty was signed in 1802 at Amiens, giving breathing space to both powers.  This however was not the end of the wars.  By 1803, war had been renewed and the Napoleonic Wars had begun.  Britain was primarily a naval power whilst Napoleonic France was a land based power.  After crowning himself emperor in 1804,, napoleon attempted to gain superiority over the English channel for long enough to transport an invasion force to Britain.  However this dream was banished by the defeat at Trafalgar in October 1805.  This defeat, as well as the unprovoked attack upon the Danish fleet in 1807, crippled the French so much so that it would not be able to seriously threaten British naval interests for a decade or more.

Napoleons decision to invade Spain and Portugal in 1808 opened up a theatre of war in which the British took advantage, sending Wellesley with an expeditionary force to combat the French and provide assistance.  This would be a serious hamper and drain on French resources over the next six years.  After napoleon’s failed invasion of Russia in 1812, a combination of powers managed to push him back in 1813 and by 1814 force him to abdicate.  His attempt to regain the throne in 1815 was defeated at the Battle of waterloo where Wellesley, now Duke of Wellington, with Prussian support smashed the French and ended the war.