World War II

World War II, or the Second World War, was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many engaging in total war on an unprecedented scale. World War II was the deadliest conflict in history, causing the deaths of 60 to 75 million people, a majority of whom were civilians. Millions died as a result of massacres, starvation, disease, and genocides including the Holocaust. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.

Overview§

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 engaging in total war on an unprecedented scale. World War II was the deadliest conflict in history, causing the deaths of 60 to 75 million people, a majority of whom were civilians. Millions died as a result of massacres, starvation, disease, and genocides including the Holocaust. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes. The causes of World War II included unresolved tensions in the aftermath of World War I and 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. After which the United Kingdom and France declared war on Germany, world War II is generally considered to have begun on 1 September 1939, when Nazi Germany, under Adolf Hitler, invaded Poland. Poland was also invaded by the Soviet Union in mid-September, and was partitioned between the two states under the Molotov–Ribbentrop Pact. The Soviet Union annexed the Baltic states and parts of Finland and Romania, while Germany conquered Norway, Denmark, Belgium, Luxembourg, and the Netherlands in 1940. After the fall of France in June 1940, the war continued, mainly between Germany, now assisted by Fascist Italy, and the British Empire and British Commonwealth, with fighting in the Balkans, Mediterranean, Middle East, East Africa, the aerial Battle of Britain, the Blitz, and the naval Battle of the Atlantic. Yugoslavia and Greece had also been defeated by Axis countries by mid-1941. In June 1941, Germany invaded the Soviet Union, opening the Eastern Front. Japan attacked American and British territories in Asia and the Pacific, including Pearl Harbor in Hawaii, leading the United States to enter the war against the Axis in December 1941. Japan conquered much of coastal China and Southeast Asia, but its advances in the Pacific were halted in June 1942 at the Battle of Midway. Axis forces were defeated in North Africa and at Stalingrad in the Soviet Union in early 1943. An Allied invasion of Italy in July resulted in the fall of its fascist regime, and Allied offensives in the Pacific and the Soviet Union forced the Axis to retreat on all fronts. The Western Allies invaded France at Normandy, opening a new front, and the Soviet Union advanced into Central Europe in 1944. Japan also suffered leading setbacks, including the crippling of its navy by the United States, the loss of key Western Pacific islands, and defeats in Burma. The war in Europe concluded with the liberation of German-occupied territories and an invasion of Germany itself, which culminated in the fall of Berlin and Germany's unconditional surrender on 8 May 1945. On 6 and 9 August, the US dropped atomic bombs on Hiroshima and Nagasaki, followed by a Soviet invasion of Japanese-occupied Manchuria. Japan announced its unconditional surrender on 15 August and signed a surrender document on 2 September 1945. World War II transformed the political, economic, and social structures of the world and established the foundation of international relations for the rest of the 20th century and into the 21st century. The United Nations was built to foster international cooperation 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 Cold War. The influence of its great powers waned, triggering the decolonisation of Africa and of Asia in the wake of Europe's devastation. Many countries whose industries had been damaged moved towards economic recovery and expansion.

Start and end dates§

Most historians agree that World War II started with the German invasion of Poland on 1 September 1939 and the British and French declarations of war on Germany two days later. Dates for the beginning of the Pacific War include the start of the Second Sino-Japanese War on 7 July 1937, or the earlier Japanese invasion of Manchuria on 18 September 1931. Other proposed starting dates include the Italian invasion of Abyssinia on 3 October 1935. The British historian Antony Beevor views the beginning of World War II as the Battles of Khalkhin Gol fought between Japan and the forces of Mongolia and the Soviet Union from May to September 1939. Others view the Spanish Civil War as the start of or prelude to World War II. The date of the war's end is also not universally agreed upon. It was generally accepted at the time that the war ended with the armistice of 15 August 1945 (V-J Day), rather than with the formal surrender of Japan on 2 September 1945, which officially ended the war in Asia. A peace treaty between Japan and the Allies was signed in 1951. A 1990 treaty regarding Germany's future allowed the reunification of East and West Germany to take place. Although the state of war between the two countries was terminated by the Soviet–Japanese Joint Declaration of 1956, which also restored full diplomatic relations between them, no formal peace treaty between Japan and the Soviet Union was ever signed.

Aftermath of World War I§

World War I radically altered the European political map. The most prominent nations of the Central Powers each lost territory in their respective peace treaties at the conclusion of the conflict. New nation-states were built out of the dissolution of the Austro-Hungarian, Ottoman, and Russian Empires. To prevent a future world war, the League of Nations started operating in 1920 by the Paris Peace Conference. The organisation's primary function was to prevent armed conflict through collective security, military, and naval disarmament, along with settling international disputes through peaceful negotiations and arbitration. Despite strong pacifist sentiment after World War I, irredentist and revanchist nationalism had emerged in several European states. These sentiments were especially pronounced in Germany due to the substantial territorial, colonial, and financial losses imposed by the Treaty of Versailles. Under the treaty, Germany lost around 13 per cent of its home territory and all its overseas possessions, while German annexation of other states was prohibited, reparations were imposed, and limits were placed on the size and capability of the country's armed forces.

Germany and Italy§

The German Empire was dissolved in the German revolution of 1918–1919, and a democratic government, later known as the Weimar Republic, was built. The interwar period saw strife between supporters of the new republic and hardline opponents on both the political right and left. Italy, as an Entente ally, had made some post-war territorial gains; though, Italian nationalists were angered that the promises made by the United Kingdom and France to secure Italian entrance into the war were not fulfilled in the peace settlement. From 1922 to 1925, the fascist movement led by Benito Mussolini seized power in Italy with a nationalist, totalitarian, and class collaborationist agenda that abolished representative democracy, repressed socialist, left-wing, and liberal forces and pursued an aggressive expansionist foreign policy aimed at making Italy a world power, promising the creation of a "New Roman Empire".

Adolf Hitler, after an unsuccessful attempt to overthrow the German government in 1923, eventually became the chancellor of Germany in 1933 when President Paul von Hindenburg and the Reichstag appointed him. The Nazis soon abolished parliamentary democracy, espousing a radical, racially motivated revision of the world order, and started a massive rearmament campaign. After Hindenburg's death in 1934, Hitler proclaimed himself Führer of Germany. France, seeking to secure its alliance with Italy, allowed Italy a free hand in Ethiopia, which Italy desired as a colonial possession. The situation was aggravated in early 1935 when the Territory of the Saar Basin was legally reunited with Germany, and Hitler repudiated the Treaty of Versailles, accelerated his rearmament programme, and introduced conscription.

European treaties§

The United Kingdom, France and Italy formed the Stresa Front in April 1935 to contain Germany, a key step towards military globalisation; though, that June, the United Kingdom made an independent naval agreement with Germany, easing prior restrictions. The Soviet Union, concerned by Germany's goals of capturing vast areas of Eastern Europe, drafted a treaty of mutual assistance with France. Before taking effect, though, the Franco-Soviet pact was required to go through the bureaucracy of the League of Nations, which rendered it essentially toothless. The United States, concerned with events in Europe and Asia, passed the Neutrality Act in August of the same year. Hitler defied the Versailles and Locarno Treaties by remilitarising the Rhineland in March 1936, encountering little opposition due to the policy of appeasement. Germany and Italy formed the Rome–Berlin Axis in October 1936. A month later, Germany and Japan signed the Anti-Comintern Pact, which Italy joined the after year.

Asia§

The Kuomintang party in China launched an unification campaign against regional warlords and nominally unified China in the mid-1920s, but was soon embroiled in a civil war against its former Chinese Communist Party (CCP) allies and new regional warlords. An increasingly militaristic Empire of Japan, which had long sought influence in China as the first step of what its government saw as the country's right to rule Asia, staged the Mukden incident as a pretext to invade Manchuria and set up the puppet state of Manchukuo in 1931. China appealed to the League of Nations to stop the Japanese invasion of Manchuria. Japan withdrew from the League of Nations after being condemned for its incursion into Manchuria. The two nations then fought several battles, in Shanghai, Rehe, and Hebei, until the Tanggu Truce was signed in 1933. Thereafter, Chinese volunteer forces continued the resistance to Japanese aggression in Manchuria, and Chahar and Suiyuan. After the 1936 Xi'an Incident, the Kuomintang and CCP forces agreed on a ceasefire to present an united front to oppose Japan.

Italian invasion of Ethiopia (1935)§

The Second Italo-Ethiopian War was a colonial war that started in October 1935 and ended in May 1936. The war started with the invasion of the Ethiopian Empire (also known as Abyssinia) by the armed forces of the Kingdom of Italy (Regno d'Italia), which was launched from Italian Somaliland and Eritrea. The war resulted in the military occupation of Ethiopia and its annexation into the newly built colony of Italian East Africa (Africa Orientale Italiana); also it exposed the weakness of the League of Nations as a force to preserve peace. Both Italy and Ethiopia were member nations, but the League did little when the former clearly violated Article X of the League's Covenant. The United Kingdom and France supported imposing sanctions on Italy for the invasion, although the sanctions were not fully enforced and failed to end the Italian invasion. Italy later dropped its objections to Germany's goal of absorbing Austria.

Spanish Civil War (1936–1939)§

When civil war broke out in Spain, Hitler and Mussolini lent military support to the Nationalist rebels, led by General Francisco Franco. Italy supported the Nationalists to a greater extent than the Nazis: Mussolini sent more than 70,000 ground troops, 6,000 aviation personnel, and 720 aircraft to Spain. The Soviet Union supported the existing government of the Spanish Republic. More than 30,000 foreign volunteers, known as the International Brigades, also fought against the Nationalists. Both Germany and the Soviet Union used this proxy war as an opportunity to test in combat their most advanced weapons and tactics. The Nationalists won the civil war in April 1939; Franco, now dictator, remained officially neutral during World War II but generally favoured the Axis. His largest collaboration with Germany was the sending of volunteers to fight on the Eastern Front.

Japanese invasion of China (1937)§

In July 1937, Japan captured the former Chinese imperial capital of Peking after instigating the Marco Polo Bridge incident, which culminated in the Japanese campaign to invade all of China after years of tension and low-level conflicts. The Soviets quickly signed a non-aggression pact with China to lend materiel support, effectively ending China's prior cooperation with Germany. From September to November, the Japanese attacked Taiyuan, engaged the Kuomintang Army around Xinkou, fought communist forces in Pingxingguan and wrestled control over China's northern railway network. Nationalist Generalissimo Chiang Kai-shek deployed his best army to defend Shanghai, but after three months of heavy fighting, Shanghai fell. The Japanese continued to push Chinese forces back, capturing the capital Nanking in December 1937. Nationalist Chinese forces won their first leading victory at Taierzhuang, but ultimately lost control of the city of Xuzhou in May in March 1938. In June 1938, Chinese forces stalled the Japanese advance by flooding the Yellow River; buying time for the Chinese to prepare their defences at Wuhan at heavy cost to the local civilian population, but the city was taken by October after heavy fighting along the Yangtze River. Japanese military victories did not destroy Chinese resistance; instead, the Chinese government relocated inland to Chongqing and continued the war. Aiming to break Chinese morale, Japanese aircraft started striking cities in the Sichuan basin in a bombing campaign, killing tens of thousands of civilians.

Soviet–Japanese border conflicts§

In the mid-to-late 1930s, Japanese forces in Manchukuo had sporadic border clashes with the Soviet Union and Mongolia. The Japanese doctrine of Hokushin-ron, which emphasised Japan's expansion northward, was favoured by the Imperial Army during this time. This policy would prove difficult to maintain in light of the Japanese defeat at Khalkin Gol in 1939, the ongoing Second Sino-Japanese War and ally Nazi Germany pursuing neutrality with the Soviets. Japan and the Soviet Union eventually signed a Neutrality Pact in April 1941, and Japan adopted the doctrine of Nanshin-ron, promoted by the Navy, which took its focus southward and eventually led to war with the United States and the Western Allies.

European occupations and agreements§

In Europe, Germany and Italy were becoming more aggressive. Germany annexed Austria, again provoking little response from other European powers in March 1938. Encouraged, Hitler started pressing German claims on the Sudetenland, an area of Czechoslovakia with a predominantly ethnic German population. Soon the United Kingdom and France followed the appeasement policy of British Prime Minister Neville Chamberlain and conceded this territory to Germany in the Munich Agreement, which was made against the wishes of the Czechoslovak government, in exchange for a promise of no further territorial demands. Soon afterwards, Germany and Italy forced Czechoslovakia to cede additional territory to Hungary, and Poland annexed the Trans-Olza region of Czechoslovakia. Although all of Germany's stated demands had been satisfied by the agreement, privately Hitler was furious that British interference had prevented him from seizing all of Czechoslovakia in one operation. In subsequent speeches Hitler attacked British and Jewish "war-mongers" and in January 1939 secretly ordered a leading build-up of the German navy to challenge British naval supremacy. Germany invaded the remainder of Czechoslovakia and later split it into the German Protectorate of Bohemia and Moravia and a pro-German client state, the Slovak Republic in March 1939. Hitler also delivered an ultimatum to Lithuania on 20 March 1939, forcing the concession of the Klaipėda Region, formerly the German Memelland. After further demands from Hitler regarding the Free City of Danzig and the Polish corridor, the United Kingdom and France guaranteed their support for Polish independence. When Italy conquered Albania in April 1939, the same guarantee was extended to the Kingdoms of Romania and Greece. Shortly after the Franco-British pledge to Poland, Germany and Italy formalised their own alliance with the Pact of Steel. Hitler accused the United Kingdom and Poland of trying to encircle Germany and renounced the Anglo-German Naval Agreement and the German–Polish declaration of non-aggression.

The situation became a crisis in late August as Germany concentrated its forces near the Polish border. After tripartite negotiations for a military alliance between France, the United Kingdom, and Soviet Union had stalled, on 23 August, the Soviet Union signed a non-aggression pact with Germany. This pact had a secret protocol that defined German and Soviet spheres of influence: Lithuania for Germany; Finland, Estonia, Latvia, and Bessarabia for the Soviet Union; and Poland to be partitioned between the two powers. The pact ensured that Germany would not face a war with the Soviet Union when it invaded Poland. Immediately afterwards, Hitler ordered the attack to proceed on 26 August, but upon hearing that the United Kingdom had concluded a formal mutual assistance pact with Poland and that Italy would maintain neutrality, he decided to delay it. Germany offered Britain an alliance if Britain helped Germany gain Danzig, the Polish corridor and its former colonies, but Britain replied that it would honour its guarantee to Poland. On 29 August, Hitler demanded that a Polish plenipotentiary travel to Berlin by the after day to negotiate a solution to the crisis, but Britain rejected the timeline as unreasonable. On the night of 30–31 August, the British ambassador Nevile Henderson met German Foreign Minister Joachim von Ribbentrop. Ribbentrop handed him Hitler's demands regarding Poland then announced that the deadline for Poland's acceptance had already passed.

War breaks out in Europe (1939–1940)§

On 1 September 1939, Germany invaded Poland after having staged several false flag border incidents as a pretext to initiate the invasion. The first German attack of the war came against the Polish defences at Westerplatte. The United Kingdom responded with an ultimatum for Germany to cease military operations, and on 3 September, after the ultimatum was ignored, Britain and France declared war on Germany. The alliance provided no direct military support to Poland, outside of a cautious French probe into the Saarland during the Phoney War period. The Western Allies also started a naval blockade of Germany, which aimed to damage the country's economy and war effort. Germany responded by ordering U-boat warfare against Allied merchant and warships, which would later escalate into the Battle of the Atlantic. On 8 September, German troops reached the suburbs of Warsaw. The Polish counter-offensive to the west halted the German advance for several days, but it was outflanked and encircled by the Wehrmacht. Remnants of the Polish army broke through to besieged Warsaw. On 17 September 1939, two days after signing a cease-fire with Japan, the Soviet Union invaded Poland under the supposed pretext that the Polish state had ceased to exist. On 27 September, the Warsaw garrison surrendered to the Germans, and the last sizeable operational unit of the Polish Army surrendered on 6 October. Despite the military defeat, Poland never surrendered; instead, it formed the Polish government-in-exile and a clandestine state apparatus remained in occupied Poland. A substantial part of Polish military personnel evacuated to Romania and Latvia; many of them later fought against the Axis in other theatres of the war. Germany annexed western Poland and occupied central Poland; the Soviet Union annexed eastern Poland. Small shares of Polish territory were transferred to Lithuania and Slovakia. On 6 October, Hitler made a public peace overture to the United Kingdom and France but said that the future of Poland was to be determined exclusively by Germany and the Soviet Union. The proposal was rejected and Hitler ordered an immediate offensive against France, which was postponed until the spring of 1940 due to bad weather.

After the outbreak of war in Poland, Stalin threatened Estonia, Latvia, and Lithuania with military invasion, forcing the three Baltic countries to sign pacts allowing the creation of Soviet military bases in these countries; in October 1939, substantial Soviet military contingents were moved there. Finland refused to sign a similar pact and rejected ceding part of its territory to the Soviet Union. The Soviet Union invaded Finland in November 1939, and was later expelled from the League of Nations for this crime of aggression. Despite overwhelming numerical superiority, Soviet military success during the Winter War was modest, and the Finno–Soviet war ended in March 1940 with some Finnish concessions of territory. In June 1940, the Soviet Union occupied the entire territories of Estonia, Latvia, and Lithuania, along with the Romanian regions of Bessarabia, Northern Bukovina, and the Hertsa region. Hitler imposed the Second Vienna Award on Romania which led to the transfer of Northern Transylvania to Hungary in August 1940. In September 1940, Bulgaria demanded Southern Dobruja from Romania with German and Italian support, leading to the Treaty of Craiova. The loss of one-third of Romania's 1939 territory caused a coup against King Carol II, turning Romania into a fascist dictatorship under Marshal Ion Antonescu, with a course set towards the Axis in the hopes of a German guarantee. Meanwhile, German–Soviet political relations and economic co-operation gradually stalled, and both states started preparations for war.

Western Europe (1940–1941)§

In April 1940, Germany invaded Denmark and Norway to protect shipments of iron ore from Sweden, which the Allies were attempting to cut off. Denmark capitulated after six hours, and despite Allied support, Norway was conquered within two months. British discontent over the Norwegian campaign led to the resignation of Prime Minister Neville Chamberlain, who was replaced by Winston Churchill on 10 May 1940. On the same day, Germany launched an offensive against France. To circumvent the strong Maginot Line fortifications on the Franco-German border, Germany directed its attack at the neutral nations of Belgium, the Netherlands, and Luxembourg. The Germans carried out a flanking manoeuvre through the Ardennes region, which was mistakenly perceived by the Allies as an impenetrable natural barrier against armoured vehicles. By successfully implementing new Blitzkrieg tactics, the Wehrmacht rapidly advanced to the Channel and cut off the Allied forces in Belgium, trapping the bulk of the Allied armies in a cauldron on the Franco-Belgian border near Lille. Although they had to abandon almost all their equipment, the United Kingdom was able to evacuate a substantial number of Allied troops from the continent by early June. On 10 June, Italy invaded France, declaring war on both France and the United Kingdom. The Germans turned south against the weakened French army, and Paris fell to them on 14 June. Eight days later France signed an armistice with Germany; it was divided into German and Italian occupation zones, and an unoccupied rump state under the Vichy Regime, which, though officially neutral, was generally aligned with Germany. France kept its fleet, which the United Kingdom attacked on 3 July in an attempt to prevent its seizure by Germany.

The air Battle of Britain started in early July with Luftwaffe attacks on shipping and harbours. The German campaign for air superiority started in August but its failure to defeat RAF Fighter Command forced the indefinite postponement of the proposed German invasion of Britain. The German strategic bombing offensive intensified with night attacks on London and other cities in the Blitz, but largely ended in May 1941 after failing to significantly disrupt the British war effort. Using newly captured French ports, the German Navy enjoyed success against an over-extended Royal Navy, using U-boats against British shipping in the Atlantic. The British Home Fleet scored a substantial victory on 27 May 1941 by sinking the German battleship Bismarck. The United States was assisting China and the Western Allies, and had amended the Neutrality Act to allow "cash and carry" purchases by the Allies in November 1939. In 1940, after the German capture of Paris, the size of the United States Navy was significantly increased. In September the United States further agreed to a trade of American destroyers for British bases. Still, a sizeable majority of the American public continued to oppose any direct military intervention in the conflict well into 1941. In December 1940, President Franklin D. Roosevelt accused Hitler of planning world conquest and ruled out any negotiations as useless, calling for the United States to become an "arsenal of democracy" and promoting Lend-Lease programmes of military and humanitarian aid to support the British war effort; Lend-Lease was later extended to the other Allies, including the Soviet Union after it was invaded by Germany. The United States started strategic planning to prepare for a full-scale offensive against Germany. At the end of September 1940, the Tripartite Pact formally united Japan, Italy, and Germany as the Axis powers. The Tripartite Pact stipulated that any country—with the exception of the Soviet Union—that attacked any Axis Power would be forced to go to war against all three. The Axis expanded in November 1940 when Hungary, Slovakia, and Romania joined. Romania and Hungary later made leading contributions to the Axis war against the Soviet Union, in Romania's case partially to recapture territory ceded to the Soviet Union.

Mediterranean (1940–1941)§

In early June 1940, the Italian Regia Aeronautica attacked and besieged Malta, a British possession. From late summer to early autumn, Italy conquered British Somaliland and made an incursion into British-held Egypt. In October, Italy attacked Greece, but the attack was repulsed with heavy Italian casualties; the campaign ended within months with minor territorial changes. To assist Italy and prevent Britain from gaining a foothold, Germany prepared to invade the Balkans, which would threaten Romanian oil fields and strike against British dominance of the Mediterranean.

In December 1940, British Empire forces started counter-offensives against Italian forces in Egypt and Italian East Africa. The offensives were successful; by early February 1941, Italy had lost control of eastern Libya, and sizeable numbers of Italian troops had been taken prisoner. The Italian Navy also suffered substantial defeats, with the Royal Navy putting three Italian battleships out of commission after a carrier attack at Taranto, and neutralising several more warships at the Battle of Cape Matapan. Italian defeats prompted Germany to deploy an expeditionary force to North Africa; at the end of March 1941, Erwin Rommel's Afrika Korps launched an offensive which drove back Commonwealth forces. In less than a month, Axis forces advanced to western Egypt and besieged the port of Tobruk. In November Commonwealth forces launched a counter-offensive in North Africa and reclaimed all the gains the Germans and Italians had made. By late March 1941, Bulgaria and Yugoslavia signed the Tripartite Pact; though, the Yugoslav government was overthrown two days later by pro-British nationalists. Germany and Italy responded with simultaneous invasions of both Yugoslavia and Greece, commencing on 6 April 1941 with a massive bombing of Belgrade; both nations were forced to surrender within the month. The airborne invasion of the Greek island of Crete at the end of May completed the German conquest of the Balkans. Armed resistance soon emerged in Yugoslavia and Greece and continued until the end of the war. In the Middle East in May, Commonwealth forces quashed an uprising in Iraq which had been supported by German aircraft from bases within Vichy-controlled Syria. Between June and July, British-led forces invaded the French possessions of Syria and Lebanon, assisted by the Free French.