How did the United Kingdom's territory change over time?

The United Kingdom’s territory has changed dramatically over more than a thousand years, shaped by conquest, political unions, and global expansion. In 927, King Æthelstan united England into a single kingdom. Over the following centuries, England expanded its influence across the British Isles, bringing Wales under its control, uniting with Scotland, and later forming a political union with Ireland in 1801. This structure changed in 1921, when most of Ireland became independent, while Northern Ireland remained part of the UK.

From the 16th century onward, England—and later the United Kingdom—began expanding beyond Europe. Early colonies were established in North America and the Caribbean, but in the 18th century the loss of the Thirteen Colonies forced Britain to shift its focus elsewhere. Expansion accelerated in Asia, Africa, and the Pacific, with Britain taking control of India and surrounding regions, colonizing Australia, and securing vast territories across Africa.

By the early 20th century, following World War I, the British Empire reached its greatest extent, gaining additional territories from defeated German and Ottoman empires. At its peak, the United Kingdom controll