Britain, France, Germany and Italy sign the Munich Agreement, allowing Germany to occupy the Sudetenland region of Czechoslovakia.

The Munich Agreement (Czech: Mnichovsk dohoda; Slovak: Mnchovsk dohoda; German: Mnchner Abkommen) was an agreement concluded at Munich on 30 September 1938, by Germany, the United Kingdom, France, and Italy. It provided "cession to Germany of the Sudeten German territory" of Czechoslovakia, despite the existence of a 1924 alliance agreement and 1925 military pact between France and the Czechoslovak Republic, for which it is also known as the Munich Betrayal (Mnichovsk zrada; Mnchovsk zrada). Most of Europe celebrated the Munich agreement, which was presented as a way to prevent a major war on the continent. The four powers agreed to the German annexation of the Czechoslovak borderland areas named the Sudetenland, where more than three million people, mainly ethnic Germans, lived. Adolf Hitler announced that it was his last territorial claim in Northern Europe.

Germany had started a low-intensity undeclared war on Czechoslovakia on 17 September 1938. In reaction, the United Kingdom and France on 20 September formally asked Czechoslovakia to cede its Sudetenland territory to Germany, which was followed by Polish territorial demands brought on 21 September and Hungarian on 22 September. Meanwhile, German forces conquered parts of Cheb District and Jesenk District and briefly overran, but were repelled from dozens of other border counties. Poland also grouped its army units near its common border with Czechoslovakia and also instigated generally unsuccessful sabotage on 23 September. Hungary also moved its troops towards the border with Czechoslovakia, without attacking.

An emergency meeting of the main European powers not including Czechoslovakia, although their representatives were present in the town, or the Soviet Union, an ally to both France and Czechoslovakia took place in Munich, Germany, on 2930 September 1938. An agreement was quickly reached on Hitler's terms, being signed by the leaders of Germany, France, Britain, and Italy. The Czechoslovak mountainous borderland that the powers offered to appease Germany had not only marked the natural border between the Czech state and the Germanic states since the early Middle Ages, but it also presented a major natural obstacle to any possible German attack. Having been strengthened by significant border fortifications, the Sudetenland was of absolute strategic importance to Czechoslovakia.

On 30 September, Czechoslovakia yielded to the combination of military pressure by Germany, Poland and Hungary, and diplomatic pressure by the United Kingdom and France, and agreed to give up territory to Germany on Munich terms. Then, on 1 October, Czechoslovakia also accepted Polish territorial demands.The Munich Agreement was soon followed by the First Vienna Award on 2 November 1938, separating largely Hungarian inhabited territories in southern Slovakia and southern Subcarpathian Rus' from Czechoslovakia. On 30 November 1938 Czechoslovakia ceded to Poland small patches of land in Spi and Orava regions.In March 1939, the First Slovak Republic, a Nazi puppet state, proclaimed its independence. Shortly afterwards, Hitler reneged on his solemn promises to respect the integrity of Czechoslovakia by invading Czechia and turning it into the Protectorate of Bohemia and Moravia, giving Germany full control of what remained of Czechoslovakia, including its significant military arsenal that later played an important role in Germany's invasions of Poland and France. As a result, Czechoslovakia had disappeared.Today, the Munich Agreement is widely regarded as a failed act of appeasement, and the term has become "a byword for the futility of appeasing expansionist totalitarian states."

The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a sovereign country in north-western Europe, off the north-­western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-­eastern part of the island of Ireland, and many smaller islands within the British Isles. Northern Ireland shares a land border with the Republic of Ireland. Otherwise, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world. The Irish Sea separates Great Britain and Ireland. The total area of the United Kingdom is 93,628 square miles (242,500 km2), with an estimated population in 2020 of over 67 million.The United Kingdom is a unitary parliamentary democracy and constitutional monarchy. The monarch, Queen Elizabeth II, has reigned since 1952. The capital and largest city is London, a global city and financial centre with a metropolitan area population of 14 million. Other major cities include Birmingham, Manchester, Glasgow, Liverpool and Leeds.

The United Kingdom consists of four countries: England, Scotland, Wales and Northern Ireland. Other than England, the constituent countries have their own devolved governments, each with varying powers.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 included Wales, annexed in 1542) and the Kingdom of Scotland in 1707 formed 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 that name in 1927.The nearby Isle of Man, Guernsey and Jersey are not part of the UK, being Crown Dependencies with the British Government responsible for defence and international representation. There are also 14 British Overseas Territories, the last remnants of the British Empire which, at its height in the 1920s, encompassed almost a quarter of the world's landmass and a third of the world's population, and was the largest empire in history. British influence can be observed in the language, culture and the legal and political systems of many of its former colonies.The United Kingdom has the world's fifth-largest economy by nominal gross domestic product (GDP), and the tenth-largest by purchasing power parity (PPP). It has a high-income economy and a very high human development index rating, ranking 13th in the world. The UK became the world's first industrialised country and was the world's foremost power during the 19th and early 20th centuries. Today the UK remains one of the world's great powers, with considerable economic, cultural, military, scientific, technological and political influence internationally. It is a recognised nuclear state and is ranked fourth globally in military expenditure. It has been a permanent member of the United Nations Security Council since its first session in 1946.

The United Kingdom is a member of the Commonwealth of Nations, the Council of Europe, the G7, the Group of Ten, the G20, the United Nations, NATO, AUKUS, the Organisation for Economic Co-operation and Development (OECD), Interpol, and the World Trade Organization (WTO). It was a member state of the European Communities (EC) and its successor, the European Union (EU), from its accession in 1973 until its withdrawal in 2020 following a referendum held in 2016.