Vichy France (French: Rgime de Vichy; 10 July 1940 9 August 1944) is the common name of the French State (tat franais) headed by Marshal Philippe Ptain during World War II. Officially independent, it adopted a policy of collaboration with Nazi Germany, which occupied its northern and western portions before occupying the remainder of Metropolitan France in November 1942. Though Paris was ostensibly its capital, the Vichy government established itself in the resort town of Vichy in the unoccupied "Free Zone" (zone libre), where it remained responsible for the civil administration of France as well as its colonies.The Third French Republic had begun the war in September 1939 on the side of the Allies. On 10 May 1940, it was invaded by Nazi Germany. The German Army rapidly broke through the Allied lines by bypassing the highly fortified Maginot Line and invading through Belgium. By mid-June, the military situation of the French was dire, and it was apparent that the battle for Metropolitan France could not be won. The French government began to discuss the possibility of an armistice. Paul Reynaud resigned as prime minister, rather than sign an armistice, and was replaced by Marshal Philippe Ptain, a hero of World War I. Shortly thereafter, Ptain signed the Armistice of 22 June 1940. On 10 July, the Third Republic was effectively dissolved as Ptain was granted dictatorial powers by the National Assembly.

At Vichy, Ptain established an authoritarian government that reversed many liberal policies and began tight supervision of the economy. Conservative Catholics became prominent, and Paris lost its avant-garde status in European art and culture. The media were tightly controlled and promoted anti-Semitism and, after Operation Barbarossa started in June 1941, anti-Bolshevism. The terms of the armistice presented certain advantages, such as keeping the French Navy and French colonial empire under French control and avoiding full occupation of the country by Germany, which maintained a degree of French independence and neutrality. Despite heavy pressure, the French government at Vichy never joined the Axis powers and even remained formally at war with Germany. Conversely, Vichy France became a collaborationist regime.

Vichy is often described as German puppet state, although it has also been argued it had an agenda of its own. Germany kept two million French prisoners-of-war and imposed forced labour (service du travail obligatoire) on young French men. French soldiers were kept hostage to ensure that Vichy would reduce its military forces and pay a heavy tribute in gold, food and supplies to Germany. French police were ordered to round up Jews and other "undesirables" such as communists and political refugees, and at least 72,500 Jews were killed as a result.Most of the French public initially supported the regime, but opinion gradually turned against the French government and the occupying German forces when it became clear that Germany was losing the war, and living conditions in France were becoming increasingly difficult. The French Resistance, working largely in concert with Charles de Gaulle's movement outside the country, increased in strength over the course of the occupation. After the Allied invasion of Normandy in June 1944 and the liberation of France later that year, the Free French Provisional Government of the French Republic (GPRF) was installed as the new national government, led by de Gaulle.

The last of the Vichy exiles were captured in the Sigmaringen enclave in April 1945. Ptain was put on trial for treason by the new Provisional Government, and sentenced to death, but that was commuted to life imprisonment by de Gaulle. Only four senior Vichy officials were tried for crimes against humanity although many others had participated in the deportation of Jews for internment in Nazi concentration camps, abuses of prisoners and severe acts against members of the Resistance.

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.