From the union with Ireland to the end of the…

From the union with Ireland to the end of the First World War
Main article: History of the United Kingdom

The Anglo-Dutch council of war before Bombardment of Algiers (1816), in which a British-Allied fleet freed 3,000 Christian slaves.
The term “United Kingdom” became official in 1801 when 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.[99]

After the defeat of France at the end of the Revolutionary and Napoleonic Wars (1792–1815), the United Kingdom emerged as the principal naval and imperial power of the 19th century (with London the largest city in the world from about 1830).[100] Unchallenged at sea, British dominance was later described as Pax Britannica (“British Peace”), a period of relative peace among the Great Powers (1815–1914) during which the British Empire became the global hegemon and adopted the role of global policeman.[101][102][103][104] By the time of the Great Exhibition of 1851, Britain was described as the “workshop of the world”.[105] From 1853 to 1856, Britain took part in the Crimean War, allied with the Ottoman Empire in the fight against the Russian Empire,[106] participating in the naval battles of the Baltic Sea known as the Åland War in the Gulf of Bothnia and the Gulf of Finla

nd, among others.[107] The British Empire was expanded to include India, large parts of Africa and many other territories throughout the world. Alongside the formal control it exerted over its own colonies, British dominance of much of world trade meant that it effectively controlled the economies of many regions, such as Asia and Latin America.[108][109] Domestically, political attitudes favoured free trade and laissez-faire policies and a gradual widening of the voting franchise. During the century, the population increased at a dramatic rate, accompanied by rapid urbanisation, causing significant social and economic stresses.[110] To seek new markets and sources of raw materials, the Conservative Party under Disraeli launched a period of imperialist expansion in Egypt, South Africa, and elsewhere. Canada, Australia and New Zealand became self-governing dominions.[111] After the turn of the century, Britain’s industrial dominance was challenged by Germany and the United States.[112] Social reform and home rule for Ireland were important domestic issues after 1900. The Labour Party emerged from an alliance of trade unions and small socialist groups in 1900, and suffragettes campaigned from before 1914 for women’s right to vote.[113]

Black-and-white photo of two dozen men in military uniforms and metal helmets sitting or standing in a muddy trench.
Infantry of the Royal Irish Rifles during the Battle of the Somme. More than 885,000 British soldiers died on the battlefields of the First World War.
Britain fought alongside France, Russia and (after 1917) the United States, against Germany and its allies in the First World War (1914–1918).[114] British armed forces were engaged across much of the British Empire and in several regions of Europe, particularly on the Western front.[115] The high fatalities of trench warfare caused the loss of much of a generation of men, with lasting social effects in the nation and a great disruption in the social order.

After the war, Britain received the League of Nations mandate over a number of former German and Ottoman colonies. The British Empire reached its greatest extent, covering a fifth of the world’s land surface and a quarter of its population.[116] Britain had suffered 2.5 million casualties and finished the war with a huge national debt.[115]