The United Kingdom has evolved from a series of annexations, unions and separations of constituent countries over several hundred years.
The Treaty of Union between the Kingdom of England (which also included Wales) and the Kingdom of Scotland in 1707 resulted in their unification to become the Kingdom of Great Britain.
Its union in 1801 with the Kingdom of Ireland created the United Kingdom of Great Britain and Ireland. Most of Ireland seceded from the UK in 1922, leaving the present United Kingdom of Great Britain and Northern Ireland, which formally adopted its name in 1927.
The UK became the world’s first industrialised country and was the foremost power during the 19th and early 20th centuries, a period of unchallenged global hegemony known as “Pax Britannica”.