Adolf Hitler in the context of "German war crimes"

World War II or the Second World War (1 September 1939 – 2 September 1945) was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks and aircraft played major roles, enabling the strategic bombing of cities and delivery of the first and only nuclear weapons ever used in war. World War II is the deadliest conflict in history, causing the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were put on trial for war crimes.

The causes of World War II included unresolved tensions in the aftermath of World War I, the rise of fascism in Europe and militarism in Japan. Key events preceding the war included Japan's invasion of Manchuria in 1931, the Spanish Civil War, the outbreak of the Second Sino-Japanese War in 1937, and Germany's annexations of Austria and the Sudetenland. World War II is generally considered to have begun on 1 September 1939, when Nazi Germany, under Adolf Hitler, invaded Poland, after which the United Kingdom and France declared war on Germany. Poland was divided between Germany and the Soviet Union under the Molotov–Ribbentrop Pact. In 1940, the Soviet Union annexed the Baltic states and parts of Finland and Romania. After the fall of France in June 1940, the war continued mainly between Germany, now assisted by Fascist Italy, and the British Empire, with fighting in the Balkans, Mediterranean, and Middle East, the aerial Battle of Britain and the Blitz, and the naval Battle of the Atlantic. Through campaigns and treaties, Germany gained control of much of continental Europe and formed the Axis alliance with Italy, Japan, and other countries. In June 1941, Germany invaded the Soviet Union, opening the Eastern Front and initially making large territorial gains.

Nazi Germany, officially the German Reich and later the Greater German Reich, was the German state between 1933 and 1945, when Adolf Hitler and the Nazi Party controlled the country, transforming it into a totalitarian dictatorship. The Third Reich, meaning "Third Realm" or "Third Empire", referred to the Nazi claim that Nazi Germany was the successor to the earlier Holy Roman Empire (800–1806) and German Empire (1871–1918). The Third Reich, which the Nazis referred to as the Thousand-Year Reich, ended in May 1945, after 12 years, when the Allies defeated Germany and entered the capital, Berlin, ending World War II in Europe.

After Hitler was appointed Chancellor of Germany in 1933, the Nazi Party began to eliminate political opposition and consolidate power. A 1934 German referendum confirmed Hitler as sole Führer (leader). Power was centralised in Hitler's person, and his word became the highest law. The government was not a co-ordinated, cooperating body, but rather a collection of factions struggling to amass power. To address the Great Depression, the Nazis used heavy military spending, extensive public works projects, including the Autobahnen (motorways) and a massive secret rearmament program, forming the Wehrmacht (armed forces), all financed by deficit spending. The return to economic stability and end of mass unemployment boosted the regime's popularity. Hitler made increasingly aggressive territorial demands, seizing Austria in the Anschluss of 1938, and the Sudetenland region of Czechoslovakia. Germany signed a non-aggression pact with the Soviet Union and invaded Poland in 1939, launching World War II in Europe. In alliance with Fascist Italy and other Axis powers, Germany conquered most of Europe by 1940 and threatened Britain.

A dictator is a political leader who possesses absolute power. A dictatorship is defined as a state ruled by a dictator. The word originated as the title of a Roman dictator elected by the Roman Senate to rule the republic in times of emergency. Like the terms "tyrant" and "autocrat", dictator came to be used almost exclusively as a non-titular term for oppressive rule. In modern usage, the term dictator is generally used to describe a leader who holds or abuses an extraordinary amount of personal power.

Dictatorships are often characterised by some of the following: suspension of elections and civil liberties; proclamation of a state of emergency; rule by decree; repression of political opponents; not abiding by the procedures of the rule of law; and the existence of a cult of personality centered on the leader. Dictatorships are often one-party or dominant-party states. A wide variety of leaders coming to power in different kinds of regimes, such as one-party or dominant-party states and civilian governments under a personal rule, have been described as dictators.

The Axis powers, originally called the Rome–Berlin Axis and also Rome–Berlin–Tokyo Axis, was the military coalition which initiated World War II and fought against the Allies. Its principal members were Nazi Germany, the Kingdom of Italy and the Empire of Japan. The Axis were united in their far-right positions and general opposition to the Allies, but otherwise lacked comparable coordination and ideological cohesion.

The Axis grew out of successive diplomatic efforts by Germany, Italy, and Japan to secure their own specific expansionist interests in the mid-1930s. The first step was the protocol signed by Germany and Italy in October 1936, after which Italian leader Benito Mussolini declared that all other European countries would thereafter rotate on the Rome–Berlin axis, thus creating the term "Axis". The following November saw the ratification of the Anti-Comintern Pact, an anti-communist treaty between Germany and Japan; Italy joined the Pact in 1937, followed by Hungary and Spain in 1939. The "Rome–Berlin Axis" became a military alliance in 1939 under the so-called "Pact of Steel", with the Tripartite Pact of 1940 formally integrating the military aims of Germany, Italy, Japan, and later followed by other nations. The three pacts formed the foundation of the Axis alliance.

The causes of World War II have been given considerable attention by historians. The immediate precipitating event was the invasion of Poland by Nazi Germany on September 1, 1939, and the subsequent declarations of war on Germany made by Britain and France, but many other prior events have been suggested as ultimate causes. Primary themes in historical analysis of the war's origins include the political takeover of Germany in 1933 by Adolf Hitler and the Nazi Party; Japanese militarism against China, which led to the Japanese invasion of Manchuria and the Second Sino-Japanese War; Italian aggression against Ethiopia, which led to the Second Italo-Ethiopian War; or military uprising in Spain, which led to the Spanish Civil War.

During the interwar period, deep anger arose in the Weimar Republic over the conditions of the 1919 Treaty of Versailles, which punished Germany for its role in World War I with heavy financial reparations and severe limitations on its military that were intended to prevent it from becoming a military power again. The demilitarisation of the Rhineland, the prohibition of German unification with Austria, and the loss of its overseas colonies as well as some 12% of the pre-war land area and population of the metropole all provoked strong currents of revanchism in German politics.

Fascist movements in Europe were the set of various fascist ideologies which were practiced by governments and political organizations in Europe during the 20th century. Fascism was born in Italy following World War I, and other fascist movements, influenced by Italian fascism, subsequently emerged across Europe. Among the political doctrines which are identified as ideological origins of fascism in Europe are the combining of a traditional national unity and revolutionary anti-democratic rhetoric which was espoused by the integral nationalist Charles Maurras and the revolutionary syndicalist Georges Sorel.

The earliest foundations of fascism in practice can be seen in the Italian Regency of Carnaro, led by the Italian nationalist Gabriele D'Annunzio, many of whose politics and aesthetics were subsequently used by Benito Mussolini and his Italian Fasces of Combat which Mussolini had founded as the Fasces of Revolutionary Action in 1914. Despite the fact that its members referred to themselves as "fascists", the ideology was based around national syndicalism. The ideology of fascism would not fully develop until 1921, when Mussolini transformed his movement into the National Fascist Party, which then in 1923 incorporated the Italian Nationalist Association. The INA established fascist tropes such as colored shirt uniforms and also received the support of important proto-fascists like D'Annunzio and nationalist intellectual Enrico Corradini.

The Balkans campaign of World War II began with the Italian invasion of Greece on 28 October 1940. In the early months of 1941, Italy's offensive had stalled and a Greek counter-offensive pushed into Albania. Germany sought to aid Italy by deploying troops to Romania and Bulgaria and attacking Greece from the east. Meanwhile, the British landed troops and aircraft to shore up Greek defences. A coup d'état in Yugoslavia on 27 March caused Adolf Hitler to order the conquest of that country.

The invasion of Yugoslavia by Germany and Italy began on 6 April 1941, simultaneously with the renewed invasion of Greece; on 11 April, Hungary joined the invasion of Yugoslavia. By 17 April the Yugoslavs had signed an armistice, and by 30 April all of mainland Greece was under German or Italian control. On 20 May Germany invaded Crete by air, and by 1 June all remaining Greek and British forces on the island had surrendered. Although it had not participated in the attacks in April, Bulgaria occupied parts of both Yugoslavia and Greece shortly thereafter for the remainder of the war in the Balkans.

The Blitz (English: 'flash') was a bombing campaign by Nazi Germany and Fascist Italy against the United Kingdom during the Second World War. It lasted for eight months, from 7 September, 1940 to 11 May, 1941. The name is a shortened form of Blitzkrieg, a term used in the popular press to describe a German style of surprise attack used during the war.

Towards the end of the Battle of Britain in 1940, daylight air superiority over the United Kingdom was contested between the Luftwaffe and the Royal Air Force. Germany began conducting mass air attacks against British cities, beginning with London, in an attempt to draw the RAF Fighter Command into a battle of annihilation. Adolf Hitler and Reichsmarschall Hermann Göring, commander-in-chief of the Luftwaffe, ordered the new policy on 6 September 1940. From 7 September 1940, London was systematically bombed by the Luftwaffe for 56 of the following 57 days and nights. The attacks included a large daylight attack against London on 15 September, a large raid on 29 December 1940 against London resulting in a firestorm known as the Second Great Fire of London, and a large raid on the night of 10–11 May 1941.

The Tripartite Pact, also known as the Berlin Pact, was an agreement between Germany, Italy, and Japan signed in Berlin on 27 September 1940 by, respectively, Joachim von Ribbentrop, Galeazzo Ciano, and Saburō Kurusu (in that order) and in the presence of Adolf Hitler. It was a defensive military alliance that was eventually joined by Hungary (20 November 1940), Romania (23 November 1940), Slovakia (24 November 1940), Bulgaria (1 March 1941), and Yugoslavia (25 March 1941). Yugoslavia's accession provoked a coup d'état in Belgrade two days later. Germany, Italy, and Hungary responded by invading Yugoslavia. The resulting Italo-German client state, known as the Independent State of Croatia, joined the pact on 15 June 1941.

The Tripartite Pact was, together with the Anti-Comintern Pact and the Pact of Steel, one of a number of agreements between Germany, Japan, Italy, and other countries of the Axis powers governing their relationship.