The United Kingdom is made up of England, Wales, Scotland and Northern Ireland. It has a long history as a major player in international affairs and fulfills an important role in the EU, UN and NATO. In 1603 Scotland came under the British Crown, and in 1707 England and Scotland agreed to unite as Great Britain. Ireland had been conquered by the early 17th century, and the 1801 British Act of Union established the United Kingdom of Great Britain and Ireland. In 1922 26 counties of Ireland gained independence from London, with the other six counties remaining in the United Kingdom of Great Britain and Northern Ireland. At the beginning of the 20th century the British Empire had been the foremost global power, stretching over one-fourth of the earth's surface. But World War I significantly weakened the United Kingdom, and the years following World War II saw the demise of the empire with many colonies gaining independence. Nevertheless, the country remains a major world economic and military power, with considerable political and cultural influence around the world. As the world's first industrialized country, the economy of the United Kingdom is one of the largest in the world as well as one of the strongest in Europe, and is considered to be a leading trading power and financial center. Despite being a major member of the EU, however, the country is not part of the euro zone and the government has said a series of economic criteria must be met before the issue can be put to a referendum.