The Battle of the Bulge, also known as the Ardennes Offensive, was a major German offensive campaign on the Western Front during World War II which took place from 16 December 1944 to 25 January 1945. It was launched through the densely forested Ardennes region between Belgium and Luxembourg towards the end of the war in Europe.

The primary military objectives were to deny further use of the Belgian port of Antwerp to the Allies and to split the Allied lines, which potentially could have allowed the Germans to encircle and destroy the four Allied forces. Nazi dictator Adolf Hitler, who by this time had assumed direct command of the German armed forces, believed that achieving these objectives would compel the Western Allies to accept a peace treaty in the Axis powers' favor. By this time, it was palpable to virtually the entire German leadership including Hitler himself that they had no realistic hope of repelling the imminent Soviet invasion of Germany unless the Wehrmacht was able to concentrate the entirety of its remaining forces on the Eastern Front, which in turn obviously required that hostilities on the Western and Italian Fronts be terminated. The Battle of the Bulge remains among the most important battles of the war, as it marked the last major offensive attempted by the Axis Powers on the Western front. After their defeat, Germany would retreat for the remainder of the war.

The Germans achieved a total surprise attack on the morning of 16 December 1944, due to a combination of Allied overconfidence, preoccupation with Allied offensive plans, and poor aerial reconnaissance due to bad weather. American forces bore the brunt of the attack. The Germans had attacked a weakly defended section of the Allied line, taking advantage of heavily overcast weather conditions that grounded the Allies' superior air forces. Fierce American resistance on the northern shoulder of the offensive, around Elsenborn Ridge, and in the south, around Bastogne, blocked German access to key roads to the northwest and west that they counted on for success. Columns of armor and infantry that were supposed to advance along parallel routes found themselves on the same roads. This congestion, and terrain that favored the defenders, threw the German advance behind schedule and allowed the Allies to reinforce the thinly placed troops.

The farthest west the offensive reached was the village of Foy-Ntre-Dame, south east of Dinant, being stopped by the U.S. 2nd Armored Division on 24 December 1944. Improved weather conditions from around 24 December permitted air attacks on German forces and supply lines, which sealed the failure of the offensive. On 26 December the lead element of Patton's U.S. Third Army reached Bastogne from the south, ending the siege. Although the offensive was effectively broken by 27 December, when the trapped units of 2nd Panzer Division made two break-out attempts with only partial success, the battle continued for another month before the front line was effectively restored to its position prior to the attack. In the wake of the defeat, many experienced German units were out of men and equipment, and the survivors retreated to the Siegfried Line.

The Germans' initial attack involved 410,000 men; just over 1,400 tanks, tank destroyers, and assault guns; 2,600 artillery pieces; and over 1,000 combat aircraft, as well as large numbers of other armored fighting vehicles (AFVs). These were reinforced a couple of weeks later, bringing the offensive's total strength to around 450,000 troops, and 1,500 tanks and assault guns. Between 63,222 and 98,000 of these men were killed, missing, wounded in action, or captured. The battle severely depleted Germany's armored forces, which remained largely unreplaced throughout the remainder of the war. German Luftwaffe personnel, and later also Luftwaffe aircraft (in the concluding stages of the engagement) also sustained heavy losses.

From among the Americans' peak strength of 610,000 troops, there were 89,000 casualties, including about 19,000 killed. The "Bulge" was the largest and bloodiest single battle fought by the United States in World War II and the third-deadliest campaign in American history.

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.