Brussels (French: Bruxelles [bysl] (listen) or [byksl] (listen); Dutch: Brussel [brsl] (listen)), officially the Brussels-Capital Region (French: Rgion de Bruxelles-Capitale; Dutch: Brussels Hoofdstedelijk Gewest), is a region of Belgium comprising 19 municipalities, including the City of Brussels, which is the capital of Belgium. The Brussels-Capital Region is located in the central portion of the country and is a part of both the French Community of Belgium and the Flemish Community, but is separate from the Flemish Region (within which it forms an enclave) and the Walloon Region. Brussels is the most densely populated and the richest region in Belgium in terms of GDP per capita. It covers 162 km2 (63 sq mi), a relatively small area compared to the two other regions, and has a population of over 1.2 million. The five times larger metropolitan area of Brussels comprises over 2.5 million people, which makes it the largest in Belgium. It is also part of a large conurbation extending towards Ghent, Antwerp, Leuven and Walloon Brabant, home to over 5 million people.Brussels grew from a small rural settlement on the river Senne to become an important city-region in Europe. Since the end of the Second World War, it has been a major centre for international politics and home to numerous international organisations, politicians, diplomats and civil servants. Brussels is the de facto capital of the European Union, as it hosts a number of principal EU institutions, including its administrative-legislative, executive-political, and legislative branches (though the judicial branch is located in Luxembourg, and the European Parliament meets for a minority of the year in Strasbourg). Because of this, its name is sometimes used metonymically to describe the EU and its institutions. The secretariat of the Benelux and the headquarters of NATO are also located in Brussels. As the economic capital of Belgium and a top financial centre of Western Europe with Euronext Brussels, it is classified as an Alpha global city. Brussels is a hub for rail, road and air traffic, and is sometimes considered, together with Belgium, as the geographic, economic and cultural crossroads of Europe. The Brussels Metro is the only rapid transit system in Belgium. In addition, both its airport and railway stations are the largest and busiest in the country.Historically Dutch-speaking, Brussels saw a language shift to French from the late 19th century. Nowadays, the Brussels-Capital Region is officially bilingual in French and Dutch, even though French is the lingua franca with over 90% of the inhabitants being able to speak it. Brussels is also increasingly becoming multilingual. English is spoken as a second language by nearly a third of the population and many migrants and expatriates speak other languages as well.Brussels is known for its cuisine and gastronomic offer (including its local waffle, its chocolate, its French fries and its numerous types of beers), as well as its historical and architectural landmarks; some of them are registered as UNESCO World Heritage Sites. Main attractions include its historic Grand Place, Manneken Pis, the Atomium, and cultural institutions such as La Monnaie/De Munt and the Museums of Art and History. Due to its long tradition of Belgian comics, Brussels is also hailed as a capital of the comic strip.

World War II or the Second World War, often abbreviated as WWII or WW2, was a global war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing military alliances: the Allies and the Axis powers. In a total war directly involving more than 100 million personnel from more than 30 countries, the major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. Aircraft played a major role in the conflict, enabling the strategic bombing of population centres and the only two uses of nuclear weapons in war. World War II was by far the deadliest conflict in human history; it resulted in 70 to 85 million fatalities, a majority being civilians. Tens of millions of people died due to genocides (including the Holocaust), starvation, massacres, and disease. In the wake of the Axis defeat, Germany and Japan were occupied, and war crimes tribunals were conducted against German and Japanese leaders.

The exact causes of World War II are debated, but contributing factors included the Second Italo-Ethiopian War, the Spanish Civil War, the Second Sino-Japanese War, the Soviet–Japanese border conflicts and rising European tensions since World War I. World War II is generally considered to have begun on 1 September 1939, when Nazi Germany, under Adolf Hitler, invaded Poland. The United Kingdom and France subsequently declared war on Germany on 3 September. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet Union had partitioned Poland and marked out their "spheres of influence" across Finland, Estonia, Latvia, Lithuania and Romania. From late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, and formed the Axis alliance with Italy and Japan (along with other countries later on). Following the onset of campaigns in North Africa and East Africa, and the fall of France in mid-1940, the war continued primarily between the European Axis powers and the British Empire, with war in the Balkans, the aerial Battle of Britain, the Blitz of the UK, and the Battle of the Atlantic. On 22 June 1941, Germany led the European Axis powers in an invasion of the Soviet Union, opening the Eastern Front, the largest land theatre of war in history.

Japan, which aimed to dominate Asia and the Pacific, was at war with the Republic of China by 1937. In December 1941, Japan attacked American and British territories with near-simultaneous offensives against Southeast Asia and the Central Pacific, including an attack on the US fleet at Pearl Harbor which resulted in the United States declaring war against Japan. Therefore the European Axis powers declared war on the United States in solidarity. Japan soon captured much of the western Pacific, but its advances were halted in 1942 after losing the critical Battle of Midway; later, Germany and Italy were defeated in North Africa and at Stalingrad in the Soviet Union. Key setbacks in 1943—including a series of German defeats on the Eastern Front, the Allied invasions of Sicily and the Italian mainland, and Allied offensives in the Pacific—cost the Axis powers their initiative and forced it into strategic retreat on all fronts. In 1944, the Western Allies invaded German-occupied France, while the Soviet Union regained its territorial losses and turned towards Germany and its allies. During 1944 and 1945, Japan suffered reversals in mainland Asia, while the Allies crippled the Japanese Navy and captured key western Pacific islands.

The war in Europe concluded with the liberation of German-occupied territories, and the invasion of Germany by the Western Allies and the Soviet Union, culminating in the fall of Berlin to Soviet troops, Hitler's suicide and the German unconditional surrender on 8 May 1945. Following the Potsdam Declaration by the Allies on 26 July 1945 and the refusal of Japan to surrender on its terms, the United States dropped the first atomic bombs on the Japanese cities of Hiroshima, on 6 August, and Nagasaki, on 9 August. Faced with an imminent invasion of the Japanese archipelago, the possibility of additional atomic bombings, and the Soviet’s declared entry into the war against Japan on the eve of invading Manchuria, Japan announced on 15 August its intention to surrender, then signed the surrender document on 2 September 1945, cementing total victory in Asia for the Allies.

World War II changed the political alignment and social structure of the globe. The United Nations (UN) was established to foster international co-operation and prevent future conflicts, with the victorious great powers—China, France, the Soviet Union, the United Kingdom, and the United States—becoming the permanent members of its Security Council. The Soviet Union and the United States emerged as rival superpowers, setting the stage for the nearly half-century-long Cold War. In the wake of European devastation, the influence of its great powers waned, triggering the decolonisation of Africa and Asia. Most countries whose industries had been damaged moved towards economic recovery and expansion. Political and economic integration, especially in Europe, began as an effort to forestall future hostilities, end pre-war enmities and forge a sense of common identity.