smart_theme=falseWorld War IIb or the Second World War (1 September 1939 – 2 September 1945) was a global conflict between two major alliances: the Allies and the Axis powers. The vast majority of the world’s countries, including all the great powers, fought as part of these military alliances. Many participating countries invested all available economic, industrial, and scientific capabilities into this total war, blurring the distinction between civilian and military resources. Aircraft played a major role, enabling the strategic bombing of population centres and delivery of the only two nuclear weapons ever used in war. It was by far the deadliest conflict in history, resulting in 70–85 million fatalities. Millions died due to genocides, including the Holocaust, as well as starvation, massacres, and disease. In the wake of Axis defeat, Germany, Austria, and Japan were occupied, and war crime tribunals were conducted against German and Japanese leaders.
The causes of the war are debated; contributing factors included the rise of fascism in Europe, the Spanish Civil War, the Second Sino-Japanese War, Soviet–Japanese border conflicts, and tensions in the aftermath of 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 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 in a military alliance called the Axis with Italy, Japan, and other countries. Following the onset of campaigns in North 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 the war in the Balkans, the aerial Battle of Britain, the Blitz of the UK, and the Battle of the Atlantic. In 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 aimed to dominate East Asia and the Asia-Pacific, and by 1937 was at war with the Republic of China. In December 1941, Japan attacked American and British territories with near-simultaneous offensives against Southeast Asia and the Central Pacific, including an attack on Pearl Harbor which resulted in the United States and the United Kingdom declaring war against Japan. The European Axis powers declared war on the US in solidarity. Japan soon conquered much of the western Pacific, but its advances were halted in 1942 after losing the critical Battle of Midway; Germany and Italy were defeated in North Africa and at Stalingrad in the Soviet Union. Key setbacks in 1943—including 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 them into strategic retreat on all fronts. In 1944, the Western Allies invaded German-occupied France, while the Soviet Union regained its territorial losses and pushed Germany and its allies back. During 1944–1945, 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; 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 refusal of Japan to surrender on the terms of the Potsdam Declaration, the US dropped the first atomic bombs on Hiroshima on 6 August and Nagasaki on 9 August. Faced with imminent invasion of the Japanese archipelago, the possibility of more atomic bombings, and the Soviet Union’s declared entry into the war against Japan on the eve of invading Manchuria, Japan announced on 10 August its intention to surrender, signing a surrender document on 2 September 1945.
World War II changed the political alignment and social structure of the world, and it set the foundation for the international order for the rest of the 20th century and into the 21st century. The United Nations was established to foster international cooperation and prevent conflicts, with the victorious great powers—China, France, the Soviet Union, the UK, and the US—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. 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.
Start and end dates
See also: List of timelines of World War II
World War II began in Europe on 1 September 19391 2 with the German invasion of Poland and the United Kingdom and France’s declaration of war on Germany two days later on 3 September 1939. Dates for the beginning of the Pacific War include the start of the Second Sino-Japanese War on 7 July 1937,3 4 or the earlier Japanese invasion of Manchuria, on 19 September 1931.5 6 Others follow the British historian A. J. P. Taylor, who stated that the Sino-Japanese War and war in Europe and its colonies occurred simultaneously, and the two wars became World War II in 1941.7 Other theorised starting dates for World War II include the Italian invasion of Abyssinia on 3 October 1935.8 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 1939.9 Others view the Spanish Civil War as the start or prelude to World War II.10 11
The exact date of the war’s end also is 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 1951.12 A 1990 treaty regarding Germany’s future allowed the reunification of East and West Germany to take place and resolved most post–World War II issues.13 No formal peace treaty between Japan and the Soviet Union was ever signed,14 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.15
History
Background
Main article: Causes of World War II
Aftermath of World War I
The League of Nations assembly, held in Geneva, Switzerland (1930).
World War I had radically altered the political European map with the defeat of the Central Powers—including Austria-Hungary, Germany, Bulgaria, and the Ottoman Empire—and the 1917 Bolshevik seizure of power in Russia, which led to the founding of the Soviet Union. Meanwhile, the victorious Allies of World War I, such as France, Belgium, Italy, Romania, and Greece, gained territory, and new nation-states were created out of the dissolution of the Austro-Hungarian, Ottoman, and Russian Empires.16
To prevent a future world war, the League of Nations was established in 1920 by the Paris Peace Conference. The organisation’s primary goals were to prevent armed conflict through collective security, military, and naval disarmament, as well as settling international disputes through peaceful negotiations and arbitration.17
Despite strong pacifist sentiment after World War I,18 irredentist and revanchist nationalism had emerged in several European states. These sentiments were especially marked in Germany because of the significant territorial, colonial, and financial losses imposed by the Treaty of Versailles. Under the treaty, Germany lost around 13 percent 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.19
Germany
The German Empire was dissolved in the German Revolution of 1918–1919, and a democratic government, later known as the Weimar Republic, was created. 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; however, 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”.20
Adolf Hitler at a German Nazi political rally in Nuremberg, August 1933
Adolf Hitler, after an unsuccessful attempt to overthrow the German government in 1923, eventually became the Chancellor of Germany in 1933 when Paul von Hindenburg and the Reichstag appointed him. Following Hindenburg’s death in 1934, Hitler proclaimed himself Führer of Germany and abolished democracy, espousing a radical, racially motivated revision of the world order, and soon began a massive rearmament campaign.21 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.22
European treaties
The United Kingdom, France and Italy formed the Stresa Front in April 1935 in order to contain Germany, a key step towards military globalisation; however, 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.23 The United States, concerned with events in Europe and Asia, passed the Neutrality Act in August of the same year.24
Hitler defied the Versailles and Locarno Treaties by remilitarising the Rhineland in March 1936, encountering little opposition due to the policy of appeasement.25 In October 1936, Germany and Italy formed the Rome–Berlin Axis. A month later, Germany and Japan signed the Anti-Comintern Pact, which Italy joined the following year.26
Asia
The Kuomintang (KMT) party in China launched a 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 allies27 and new regional warlords. In 1931, an increasingly militaristic Empire of Japan, which had long sought influence in China28 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 establish the puppet state of Manchukuo.29
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.30 After the 1936 Xi’an Incident, the Kuomintang and communist forces agreed on a ceasefire to present a united front to oppose Japan.31
Pre-war events
Italian invasion of Ethiopia (1935)
Main article: Second Italo-Ethiopian War
Benito Mussolini inspecting troops during the Italo-Ethiopian War, 1935
The Second Italo-Ethiopian War was a brief colonial war that began in October 1935 and ended in May 1936. The war began 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.32 The war resulted in the military occupation of Ethiopia and its annexation into the newly created colony of Italian East Africa (Africa Orientale Italiana, or AOI); in addition 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.33 The United Kingdom and France supported imposing sanctions on Italy for the invasion, but the sanctions were not fully enforced and failed to end the Italian invasion.34 Italy subsequently dropped its objections to Germany’s goal of absorbing Austria.35
Spanish Civil War (1936–1939)
Main article: Spanish Civil War
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.36 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.37 His greatest collaboration with Germany was the sending of volunteers to fight on the Eastern Front.38
Japanese invasion of China (1937)
Main article: Second Sino-Japanese War
Imperial Japanese Army soldiers during the Battle of Shanghai, 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.39 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,40 and fought Communist forces in Pingxingguan.41 42 Generalissimo Chiang Kai-shek deployed his best army to defend Shanghai, but after three months of fighting, Shanghai fell. The Japanese continued to push Chinese forces back, capturing the capital Nanking in December 1937. After the fall of Nanking, tens or hundreds of thousands of Chinese civilians and disarmed combatants were murdered by the Japanese.43 44
In March 1938, Nationalist Chinese forces won their first major victory at Taierzhuang, but then the city of Xuzhou was taken by the Japanese in May.45 In June 1938, Chinese forces stalled the Japanese advance by flooding the Yellow River; this manoeuvre bought time for the Chinese to prepare their defences at Wuhan, but the city was taken by October.46 Japanese military victories did not bring about the collapse of Chinese resistance that Japan had hoped to achieve; instead, the Chinese government relocated inland to Chongqing and continued the war.47 48
Soviet–Japanese border conflicts
Main article: 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 War49 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.50 51
European occupations and agreements
Chamberlain, Daladier, Hitler, Mussolini, and Ciano pictured just before signing the Munich Agreement, 29 September 1938
In Europe, Germany and Italy were becoming more aggressive. In March 1938, Germany annexed Austria, again provoking little response from other European powers.52 Encouraged, Hitler began 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.53 Soon afterwards, Germany and Italy forced Czechoslovakia to cede additional territory to Hungary, and Poland annexed the Trans-Olza region of Czechoslovakia.54
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 major build-up of the German navy to challenge British naval supremacy. In March 1939, Germany invaded the remainder of Czechoslovakia and subsequently split it into the German Protectorate of Bohemia and Moravia and a pro-German client state, the Slovak Republic.55 Hitler also delivered an ultimatum to Lithuania on 20 March 1939, forcing the concession of the Klaipėda Region, formerly the German Memelland.56
German Foreign Minister Joachim von Ribbentrop (right) and the Soviet leader Joseph Stalin, after signing the Molotov–Ribbentrop Pact, 23 August 1939
Greatly alarmed and with Hitler making further demands on the Free City of Danzig, 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.57 Shortly after the Franco-British pledge to Poland, Germany and Italy formalised their own alliance with the Pact of Steel.58 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.59
The situation became a crisis in late August as German troops continued to mobilise against the Polish border. On 23 August the Soviet Union signed a non-aggression pact with Germany,60 after tripartite negotiations for a military alliance between France, the United Kingdom, and Soviet Union had stalled.61 This pact had a secret protocol that defined German and Soviet “spheres of influence” (western Poland and Lithuania for Germany; eastern Poland, Finland, Estonia, Latvia and Bessarabia for the Soviet Union), and raised the question of continuing Polish independence.62 The pact neutralised the possibility of Soviet opposition to a campaign against Poland and assured that Germany would not have to face the prospect of a two-front war, as it had in World War I. 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.63
In response to British requests for direct negotiations to avoid war, Germany made demands on Poland, which served as a pretext to worsen relations.64 On 29 August, Hitler demanded that a Polish plenipotentiary immediately travel to Berlin to negotiate the handover of Danzig, and to allow a plebiscite in the Polish Corridor in which the German minority would vote on secession.64 The Poles refused to comply with the German demands, and on the night of 30–31 August in a confrontational meeting with the British ambassador Nevile Henderson, Ribbentrop declared that Germany considered its claims rejected.65
Course of the war
For a chronological guide, see List of timelines of World War II.
See also: Diplomatic history of World War II and World War II by country
War breaks out in Europe (1939–1940)
Main article: European theatre of World War II
.jpg)
Soldiers of the German Wehrmacht tearing down the border crossing into Poland, 1 September 1939
On 1 September 1939, Germany invaded Poland after having staged several false flag border incidents as a pretext to initiate the invasion.66 The first German attack of the war came against the Polish defenses at Westerplatte.67 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,68 followed by Australia, New Zealand, South Africa, and Canada. During the Phoney War period, the alliance provided no direct military support to Poland, outside of a cautious French probe into the Saarland.69 The Western Allies also began a naval blockade of Germany, which aimed to damage the country’s economy and war effort.70 Germany responded by ordering U-boat warfare against Allied merchant and warships, which would later escalate into the Battle of the Atlantic.71
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 Poland72 under the supposed pretext that the Polish state had ceased to exist.73 On 27 September, the Warsaw garrison surrendered to the Germans, and the last large 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.74 A significant part of Polish military personnel evacuated to Romania and Latvia; many of them later fought against the Axis in other theatres of the war.75
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 rejected65 and Hitler ordered an immediate offensive against France,76 which was postponed until the spring of 1940 due to bad weather.77 78 79
Mannerheim Line and Karelian Isthmus on the last day of the Winter War, 13 March 1940
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, significant Soviet military contingents were moved there.80 81 82 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 1939,83 and was subsequently expelled from the League of Nations for this crime of aggression.84 Despite overwhelming numerical superiority, Soviet military success during the Winter War was modest,85 and the Finno-Soviet war ended in March 1940 with some Finnish concessions of territory.86
In June 1940, the Soviet Union occupied the entire territories of Estonia, Latvia and Lithuania,81 as well as the Romanian regions of Bessarabia, Northern Bukovina, and the Hertsa region. In August 1940, Hitler imposed the Second Vienna Award on Romania which led to the transfer of Northern Transylvania to Hungary.87 In September 1940, Bulgaria demanded Southern Dobruja from Romania with German and Italian support, leading to the Treaty of Craiova.88 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.89 Meanwhile, German-Soviet political relations and economic co-operation90 91 gradually stalled,92 93 and both states began preparations for war.94
Western Europe (1940–1941)
Main article: Western Front (World War II)
German advance into Belgium and Northern France, 10 May – 4 June 1940, swept past the Maginot Line (shown in dark red)
In April 1940, Germany invaded Denmark and Norway to protect shipments of iron ore from Sweden, which the Allies were attempting to cut off.95 Denmark capitulated after six hours, and despite Allied support, Norway was conquered within two months.96 British discontent over the Norwegian campaign led to the resignation of Prime Minister Neville Chamberlain, who was replaced by Winston Churchill on 10 May 1940.97
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.98 The Germans carried out a flanking manoeuvre through the Ardennes region,99 which was mistakenly perceived by the Allies as an impenetrable natural barrier against armoured vehicles.100 101 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. The United Kingdom was able to evacuate a significant number of Allied troops from the continent by early June, although they had to abandon almost all their equipment.102
On 10 June, Italy invaded France, declaring war on both France and the United Kingdom.103 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,104 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.105
London seen from St Paul’s Cathedral after the German Blitz, 29 December 1940
The air Battle of Britain106 began in early July with Luftwaffe attacks on shipping and harbours.107 The United Kingdom rejected Hitler’s peace offer,108 and the German air superiority campaign started in August but failed to defeat RAF Fighter Command, forcing 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 1941109 after failing to significantly disrupt the British war effort.107
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.110 The British Home Fleet scored a significant victory on 27 May 1941 by sinking the German battleship Bismarck.111
In November 1939, 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.112 In 1940, following 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.113 Still, a large majority of the American public continued to oppose any direct military intervention in the conflict well into 1941.114 In December 1940, 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.108 The United States started strategic planning to prepare for a full-scale offensive against Germany.115
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.116 The Axis expanded in November 1940 when Hungary, Slovakia, and Romania joined.117 Romania and Hungary later made major contributions to the Axis war against the Soviet Union, in Romania’s case partially to recapture territory ceded to the Soviet Union.118