On 1 May 1707, the united Kingdom of Great Britain was created by the political union of the Kingdom of England and the Kingdom of Scotland. This event was the result of the Treaty of Union that was agreed on 22 July 1706, and then ratified by both the Parliament of England and Parliament of Scotland each passing an Act of Union in 1707.The kingdoms of England and Scotland, together with the kingdom of Ireland, had already been in a personal union as a result of the Union of the Crowns in 1603, when James VI, King of Scots inherited the Kingdoms of England and Ireland and moved his court from Edinburgh to London. However, until 1707, all three remained separate political entities and retained their separate political institutions.Almost a century later the Kingdom of Ireland merged with the Kingdom of Great Britain to form the United Kingdom of Great Britain and Ireland with the passing of the Act of Union 1800.In this way, the United Kingdom became the union of the kingdoms of England, Ireland and Scotland.Disputes within Ireland over the terms of Irish Home Rule led eventually to the partition of the island in 1921,with Dominion status for the Irish Free State in 1922 while Northern Ireland remained part of the UK.As a result, in 1927, the formal title of the UK was changed to its current form, the United Kingdom of Great Britain and Northern Ireland.
In the 18th century, the United Kingdom played an important role in developing Western ideas of the parliamentary system as well as making significant contributions to literature, the arts, and science. The UK-led Industrial Revolution transformed the country and fuelled the growing British Empire. During this time the UK, like other great powers, was involved in colonial exploitation, including the Atlantic slave trade, although with the passing of the Slave Trade Act in 1807 the UK took a leading role in combating the trade in slaves.
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 to 1930)and remained a foremost power into the mid 20th century.Beside Russia, France and (after 1917) the USA, the British were one of the major powers opposing Germany and its allies in World War I (1914–18).Engaged in much of its empire, several regions in
Europe and increasingly taking a major role on the Western front, the armed forces grew to over five million people. The nation suffered an estimated two and a half million casualties and finished the war with a huge national debt. After the war the United Kingdom received the League of Nations mandate over former German and Ottoman colonies and the British Empire had expanded to its greatest extent, covering a fifth of the world’s land surface and a quarter of its population. The Great Depression (1929–32) occurred at a time when the UK was still far from having recovered from the effects of the war and led to hardship and political and social unrest.