sing of the Slave Trade Act of 1807 the UK took a leading role in battling the trade in slaves. The colonies in North America had been the main focus of British colonial activity. With their loss in the American War of Independence, imperial ambition turned elsewhere, particularly to India.
In 1800, while the wars with France still raged, the Parliaments of Great Britain and Ireland each passed an Act of Union, uniting the two kingdoms and creating the United Kingdom of Great Britain and Ireland, which came into being on 1 January 1801.
Waterloo marked the end of the Napoleonic Wars and the start of Pax Britannica.
After the defeat of France in the Revolutionary and Napoleonic Wars (1792–1815), the UK emerged as the principal naval and economic power of the 19th century (with London the largest city in the world from about 1830) Unchallenged at sea, Britain adopted the role of global policeman, a state of affairs later known as the Pax Britannica. It was also a period of rapid economic, colonial, and industrial growth. Britain was described as the "workshop of the world", and the British Empire grew to include India, large parts of Africa, and many other territories. Alongside the formal control it exerted over its own colonies, Britain's dominant position in world trade meant that it effectively controlled the economies of many countries, such as China, Argentina and Siam. Domestically, there was a shift to free trade and laissez-faire policies and a very significant widening of the voting franchise. The country experienced a huge population increase during the century, accompanied by rapid urbanisation, causing significant social and economic stresses. By the end of the century, other states began to challenge Britain's industrial dominance.
The UK, along with Russia, France and (after 1917) the US, was one of the major powers opposing the German Empire and its allies in World War I (1914–18). The UK armed forces grew to over five
