History of World War II

The German Empire was dissolved in the German Revolution 1918-1919, and a Weimer Republic was created.

The Paris Peace Conference was the meeting of the Allies after the end of world war I to set the peace terms on the defeated Central Powers. The Conference formally opened on 18 January 1919. Five major peace treaties were prepared in Paris Peace Conference: - Treaty of Versailles (28 June 1919) - Treaty of Saint-Germain (10 September 1919) - Treaty on Neuilly (27 November 1919) - Treaty of Trianon (4 June 1920) - Treaty of Sèvres (10 August 1920), subsequently revised by the Treaty of Lausanne (24 July 1923).

World War I ended on 11 November 1919.

The League of Nations was the first worldwide international organization whose principle mission to maintain world peace. It was founded on 10 January 1920 following the Paris Peace Conference that ended World War I, and the headquarters was in Geneva, Switzerland.

Under the Treaty of Versailles, Germany lost around 13 percent of its home territory and all its overseas possessions, limits were placed on the size and and capability of the country's armed forces.

From 1922, the Fascist movement led by Bonito Mussolini controlled power in Italy, with agenda to eradicate representative democracy, Promising to create "New Roman Empire".

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 allies and new regional warlords.

In 1931 Empire of Japan staged the Mukden Incident as a pretext to invade Manchuria.

China appealed to the League of Nations to stop the Japanese invasion of Manchuria.

Adolf Hitler, after an unsuccessful attempt to overthrow German government in 1923, he became the Chancellor in 30 January 1933.

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.

The United Kingdom, France and Italy formed the Stresa Front in April 1935 to declare the independence of Austria "would continue to inspire there common policy''. The signatories also agreed to resist any future attempt by Germany to change the Treaty of Versailles.

The Soviet Union 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 Franco-Soviet Treaty of Mutual Assistance was a bilateral treaty between France and the Soviet Union with the aim of enveloping Nazi Germany in 1935 in order to reduce the threat from central Europe. The pact was concluded in Paris on May 2, 1935 and ratified by the French government in February 1936.

The United Kingdom made an Anglo-German Naval Agreement regulating the size of Kreigsmarine in relation to the United Kingdom's Royal Navy.

The United States, concerned with events in Europe and Asia, passed the Neutrality Act at August 1935. The 1935 act, signed on August 31, 1935, imposed a general embargo on trading in arms and war materials with all parties in a war. It also declared that American citizens traveling on warring ships traveled at their own risk.

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 by the armed forces of the Kingdom of Italy. The war resulted in the military occupation of Ethiopia and its annexation into the newly created colony of Italian East Africa.

Hitler defied the Versailles and Locarno treaties by re-militarizing the Rhineland in March 1936, encountering little opposition due to appeasement. The re-militarization of the Rhineland began on 7 March 1936 when German military forces entered the Rhineland.

In October 1936, Germany and Italy formed the Rome–Berlin Axis.

Germany and Japan signed the Anti-Comintern Pact in 25 November 1936.

After the 1936 Xi'an Incident, the Kuomintang and communist forces agreed on a ceasefire to present a united front to oppose Japan.

Japan captured the former Chinese imperial capital of Peking as a result of Marco Polo Bridge Incident.

Soviets signed a non-aggression pact with China to lend material support, ending China's co-operation with Germany.

Generalissimo Chiang Kai-shek deployed his best army to defend Shanghai, but, after three months of fighting, Shanghai fell.

The Japanese continued to push the Chinese forces back, capturing the capital Nanjing in December 1937.

In March 1938, Germany annexed Austria.

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.

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.

Hitler also delivered 20 March 1939 ultimatum to Lithuania, forcing the concession of the Klaipėda Region, formerly the German Memelland.

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.

The Nationalists won the Spanish Civil War in April 1939.

Italy conquered Albania in April 1939.

After the Franco-British pledge to Poland, Germany and Italy formalized their own alliance with the Pact of Steel.

The situation reached a general crisis in late August as German troops continued to mobilize against the Polish border. On 23 August, when tripartite negotiations about a military alliance between France, the United Kingdom and Soviet Union stalled, the Soviet Union signed a non-aggression pact with Germany. The Treaty of Non-Aggression between Germany and the Union of Soviet Socialist Republics was a non-aggression pact between Nazi Germany and the Soviet Union that enabled those two powers to divide-up Poland between them.

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.

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.

The Poles refused to comply with the German demands, and on the night of 30–31 August in a stormy meeting with the British ambassador Neville Henderson, Ribbentrop declared that Germany considered its claims rejected.

On 1 September 1939, Germany invaded Poland after having staged several false flag border incidents as a pretext to initiate the attack.

The Battle of Westerplatte is often described as the first battle of the war. Beginning from 1 August till 7 August.

The United Kingdom responded with an ultimatum to Germany to cease military operations, and on 3 September, after the ultimatum was ignored, France and Britain, along with their empires, declared war on Germany. The alliance provided no direct military support to Poland, outside of a cautious French probe into the Saarland.

On 8 September, German troops reached the suburbs of Warsaw. Sight of Warsaw lasted from 8 to 28 September, Germany occupied Warsaw until 1945.

The Polish counter offensive to the west halted the German advance for several days, but it was outflanked and encircled by the Wehrmacht. The Battle of the Bzura fought between 9 and 19 September 1939, It began as a Polish counter-offensive, but ended with German victory, German forces took all of western Poland.

Soviets signed ceasefire with Japan.

Soviets invaded Poland from the east. The military operations lasted from 17 September to 6 October. Parting Poland to two divisions, division is ruled by Nazi Germany and the other by the Soviets.

Japan launched its first attack against Changsha, a strategically important Chinese city, but was repulsed by late September.

In November 1939, the United States was taking measures to assist China and the Western Allies, and amended the Neutrality Act to allow "cash and carry" purchases by the Allies. Cash and carry was a policy by US President Franklin Delano Roosevelt announced at a joint session of the United States Congress on September 21, 1939, subsequent to the outbreak of war in Europe. It replaced the Neutrality Acts of 1937, by which belligerents could purchase only nonmilitary goods from the United States as long as the recipients paid immediately in cash and assumed all risk in transportation using their own ships.

The Soviet Union forced the Baltic countries—Estonia, Latvia and Lithuania, the states that were in the Soviet "sphere of influence" under the Molotov-Ribbentrop pact—to sign "mutual assistance pacts" that stipulated stationing Soviet troops in these countries.

The Battle of Kock was the final battle in the invasion of Poland by the German at the beginning of World War II in Europe. It took place between 2–5 October 1939, near the town of Kock, in Poland.

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 would be postponed until the spring of 1940 due to bad weather.

The last large operational unit of the Polish Army (Independent Operational Group Polesie) surrendered on 6 October, after the battle of Kock. Germany annexed the western and occupied the central part of Poland, and the Soviet Union annexed its eastern part; small shares of Polish territory were transferred to Lithuania and Slovakia.

Chinese nationalist forces launched a large-scale counter-offensive in November 1939. The 1939–40 Winter Offensive was one of the major engagements between the National Revolutionary Army and Imperial Japanese Army during the Second Sino-Japanese War, in which Chinese forces launched their first major counter-offensive on multiple fronts. Although this offensive failed to achieve its original objectives, some studies have shown that it came as a heavy blow to the Japanese forces, as well as a massive shock to the Japanese military command, which did not expect the Chinese forces to be able to launch an offensive operation on such a large scale.

Finland refused to sign a similar pact and rejected ceding part of its territory to the Soviet Union. The Soviet Union invaded Finland in 30 November 1939, and the war ended 13 March 1940.

Soviet Union was expelled from the League of Nations.

In October Italy attacked Greece, but the attack was repulsed with heavy Italian casualties; the campaign ended within months with minor territorial changes. The Greco-Italian War took place between Italy and Greece from 28 October 1940 to 23 April 1941. This local war began the Balkans Campaign of World War II between the Axis powers and the Allies. It turned into the Battle of Greece when British and German ground forces intervened early in 1941.

Italian defeats prompted Germany to deploy an expeditionary force to North Africa. Operation Sonnenblaume (6 February - 25 May) was the name given to the dispatch of German troops to North Africa in February 1941, The Italian 10th Army had been destroyed by the British and Allied Western Desert Force attacks during Operation Compass (9 December 1940 – 9 February 1941). Sonnenblume succeeded because the ability of the Germans to mount an offensive was underestimated by General Archbald Wavell, the Commander in Chief Middle East, the War Office and by Winston Churchill.

Operation Wilfred was a British naval operation during the Second World War that involved the mining of the channel between Norway and her offshore islands to prevent the transport of Swedish iron ore through neutral Norwegian waters to be used to sustain the German war effort. The Allies assumed that Wilfred would provoke a German response in Norway and prepared a separate operation known as Plan R 4 to occupy Narvik and other important locations. On 8 April 1940, the operation was partly carried out, but was overtaken by events as a result of the following day′s German invasion of Norway and Denmark (Operation Weserübung), which began the Norwegian Campaign.

The Norwegian campaign was an attempted Allied occupation of northern Norway, during the early stages of World War II. Resulted evacuation of the Norwegian government and the royal family, establishment of the Norwegian armed forces from the exile. The 62 days of fighting made Norway the nation that withstood a German land invasion for the second longest period of time, after the Soviet Union.

In April 1940, Germany invaded Denmark and Norway to protect shipments of iron ore from Sweden, which the Allies were attempting to cut off. The operation lasted from 9 April to 10 June 1940.

The Norway Debate, sometimes called the Narvik Debate, was a momentous debate in the British House of Commons during the Second World War from 7 to 9 May 1940. It has been called the most far-reaching parliamentary debate of the twentieth century. At the end of the second day, the members held a vote of no confidence which was won by the government, but with a drastically reduced majority.

On 10 May, Neville Chamberlain resigned as prime minister.

Winston Churchill appointed the prime minster of the United Kingdom.

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.

Germany invaded Greece in May 1940, to join the Italian forces in Battle of Greece (28 October 1940 – 1 June 1941), resulting Axis occupation of Greece.

On 10 June, Italy invaded France, declaring war on both France and the United Kingdom. It was the first major engagement of the World War II.

In early June 1940 the Italian Royal Air Forces attacked and besieged Malta, a British possession. The siege lasted from June 1940 to November 1942, the fight for the control of the strategically important island of the British Crown Colony of Malta, which pitted the air forces and navies of Fascist Italy and Nazi Germany against the Royal Air Force (RAF) and the Royal Navy. By May 1943, the Allied forces had sunk 230 Axis ships in 164 days, the highest Allied sinking rate of the war. The Allied victory in Malta played a major role in the eventual Allied success in North Africa.

German soldiers marched past the Arch de Triomphe after the surrender of Paris.

On 22 June, the Second Armistice at Compiègne was signed by France and Germany. The Armistice of 22 June 1940 was signed at 18:35 near Compiègne, France, by officials of Nazi Germany and the French Third Republic. It did not come into effect until after midnight on 25 June.

Romania and Hungary would make major contributions to the Axis war against the Soviet Union, in Romania's case partially to recapture territory ceded to the Soviet Union. The Soviet occupation of Bessarabia and northern Bukovina took place during June, 28–July 4, 1940 as a result of the Soviet Union ultimatum given to Romania on June 26, 1940, under the threat of the use of force.

France kept its fleet, which the United Kingdom attacked on 3 July in an attempt to prevent its seizure by Germany.

The Battle of Britain began in early July with Luftwaffe attacks on shipping and harbors. The United Kingdom rejected Hitler's ultimatum, 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 Battle lasted from 10 July to 31 October.

In late summer through early autumn Italy conquered British Somaliland from 3 to 19 August 1940.

In August, Chinese communists launched an offensive in Central China. The Hundred Regiments Offensive took place between 20 August to 5 December 1941, was a major campaign of the Communist Party of China's National Revolutionary Army divisions commanded by Peng Dehuai against the Imperial Japanese Army in Central China. The battle had long been the focus of propaganda in the history of Chinese Communist Party but had become Peng Dehuai's "crime" during the Cultural Revolution. Certain issues regarding its launching and consequences are still controversial.

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.

The Italian invasion of Egypt (Operazione E) was an offensive in the Second World War, against British, Commonwealth and Free French forces in Egypt. The invasion by the Italian 10th Army (10ª Armata) ended border skirmishing on the frontier and began the Western Desert Campaign (1940–1943) proper. The goal of the Italian forces in Libya was to seize the Suez Canal by advancing along the Egyptian coast. After numerous delays, the scope of the offensive was reduced to an advance as far as Sidi Barrani, with attacks on British forces in the area. It lasted from 9 September to 16 September.

To increase pressure on China by blocking supply routes, and to better position Japanese forces in the event of a war with the Western powers, Japan invaded and occupied northern Indochina. Afterwards, the United States embargoed iron, steel and mechanical parts against Japan.

At the end of September 1940, the Tripartite Pact formally united Japan, Italy, and Germany as the Axis Powers.

The Royal Navy launched the first all-aircraft ship-to-ship naval attack in history, employing 21 Fairey Swordfish biplane torpedo bombers from the aircraft carrier HMS Illustrious in the Mediterranean Sea. The attack struck the battle fleet of the Regia Marina (Italian Military Navy) at anchor in the harbor of Taranto, using aerial torpedoes despite the shallowness of the water. The Battle took place in the night of 11-12 November 1940.

The Axis expanded in November 1940 when Hungary, Slovakia and Romania joined. Romania and Hungary would make major contributions to the Axis war against the Soviet Union, in Romania's case partially to recapture territory ceded to the Soviet Union.

On 20 November, a new government under Hideki Tojo presented an interim proposal as its final offer. It called for the end of American aid to China and for lifting the embargo on the supply of oil and other resources to Japan. In exchange, Japan promised not to launch any attacks in Southeast Asia and to withdraw its forces from southern Indochina.

In November 1940, negotiations took place to determine if the Soviet Union would join the Tripartite Pact. The Soviets showed some interest but asked for concessions from Finland, Bulgaria, Turkey, and Japan that Germany considered unacceptable.

In December 1940, British Empire forces began counter-offensives against Italian forces in Egypt and Italian East Africa. The offensives were highly successful. Operation Compass was the first large British military operation of the Western Desert Campaign (1940–1943) during the Second World War, and took place between 9 December 1940 to 9 February 1941.

On 18 December 1940, Hitler issued the directive to prepare for an invasion of the Soviet Union.

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".

Continued antipathy between Chinese communist and nationalist forces culminated in armed clashes in January 1941, effectively ending their co-operation. New Fourth Army incident was argued as a punishment of Communist insubordination and Nationalist treachery.

Since early 1941 the United States and Japan had been engaged in negotiations in an attempt to improve their strained relations and end the war in China. During these negotiations, Japan advanced a number of proposals which were dismissed by the Americans as inadequate. At the same time the United States, the United Kingdom, and the Netherlands engaged in secret discussions for the joint defence of their territories, in the event of a Japanese attack against any of them.

By March 1941, Bulgaria and Yugoslavia signed the Tripartite Pact.

Roosevelt promoted Lend-Lease programmes of aid to support the British war effort.

In March, the Japanese 11th army attacked the headquarters of the Chinese 19th army but was repulsed during Battle of Shanggao.

Ships of the Royal Navy and Royal Australian Navy, intercepted and sank or severely damaged several ships of the Italian Regia Marina under Squadron-Vice-Admiral Angelo Iachino. The Battle of Cape Matapan fought from 27 to 29 March 1941.

The Yugoslav government was overthrown two days later (Tripartite Pact Signature) by nationalists. The Yugoslav coup d'état of 27 March 1941 in Belgrade, Kingdom of Yugoslavia, replaced the regency led by Prince Paul and installed King Peter II.

Germany responded with simultaneous invasion of Yugoslavia. It was Known as the April War or Operation 25, which occurred between 6 to 18 April. The attack led to German occupation to Yugoslavia.

Although the Axis victory was swift, bitter and large-scale partisan warfare subsequently broke out against the Axis occupation of Yugoslavia, which continued until the end of the war (6 April 1941 – 25 May 1945).

The Siege of Tobruk lasted for 241 days in 1941, after Axis forces advanced through Cyrenaica from El Agheila in Operation Sonnenblume against Allied forces in Libya, during the Western Desert Campaign (1940–1943) of the Second World War. The siege diverted Axis troops from the frontier and the Tobruk garrison repulsed several Axis attacks.

With the Soviets wary of mounting tensions with Germany and the Japanese planning to take advantage of the European War by seizing resource-rich European possessions in Southeast Asia, the two powers signed the Soviet–Japanese Neutrality Pact in April 1941.

The Anglo–Iraqi War occurred from 2 to 31 May 1941, was a British-led Allied military campaign against Iraq under Rashid Ali, who had seized power during the Second World War with assistance from Germany and Italy. The campaign resulted in the downfall of Ali's government, the re-occupation of Iraq by the United Kingdom, and the return to power of the Regent of Iraq, Prince 'Abd al-Ilah, an ally to the United Kingdom.

Operation Brevity was a limited offensive conducted in mid-May 1941, during the Western Desert Campaign of the Second World War. Conceived by the commander-in-chief of the British Middle East Command, General Archibald Wavell, Brevity was intended to be a rapid blow against weak Axis front-line forces in the Sollum–Capuzzo–Bardia area of the border between Egypt and Libya. Although the operation got off to a promising start, throwing the Axis high command into confusion, most of its early gains were lost to local counter-attacks, and with German reinforcements being rushed to the front the operation was called off after one day.

The Battle of Crete was fought on the Greek island of Crete, It began on the morning of 20 May 1941, when Nazi Germany began an airborne invasion of Crete. Greek and other Allied forces, along with Cretan civilians, defended the island.

The Kiev offensive was overwhelmingly successful, resulting in encirclement and elimination of four Soviet armies, The First Battle of Kiev occurred from 23 August to 26 September, resulting German occupation to Kiev.

The British Home Fleet scored a significant victory on 27 May 1941 by sinking the German battleship Bismarck.

Between June and July, United Kingdom invaded and occupied the French possessions Syria and Lebanon (8 June – 14 July 1941), with the assistance of the Free French.

On 22 June 1941, Germany, supported by Italy and Romania, invaded the Soviet Union in Operation Barbarossa, with Germany accusing the Soviets of plotting against them. They were joined shortly by Finland and Hungary.

During the summer, the Axis made significant gains into Soviet territory, inflicting immense losses in both personnel and materiel. By mid-August, however, the German Army High Command decided to suspend the offensive of a considerably depleted Army Group Centre, and to divert the 2nd Panzer Group to reinforce troops advancing towards central Ukraine and Leningrad. The First Battle of Smolensk was fought around the city of Smolensk between 10 July and 10 September 1941, about 400 km (250 mi) west of Moscow.

In July, the UK and the Soviet Union formed a military alliance against Germany.

In August, the United Kingdom and the United States jointly issued the Atlantic Charter, which outlined British and American goals for the war, even though America had yet to officially join.

The British and Soviets invaded neutral Iran to secure the Persian Corridor and Iran's oil fields. The invasion took place from 25 to 31 August.

In September, Japan attempted to take the city of Changsha again and clashed with Chinese nationalist forces.

The siege of Leningrad was a military blockade undertaken from the south by the Army Group North of Nazi Germany against the Soviet city of Leningrad (now Saint Petersburg). The siege began on the 8 September 1941, when the Wehrmacht severed the last road to the city. Although Soviet forces managed to open a narrow land corridor to the city on 18 January 1943, the Red Army did not lift the siege until 27 January 1944, 872 days after it began.

Japan was planning an invasion of the Soviet Far East (Plan Kantokuen), intending to capitalize off the German invasion in the west, the plan cancelled on 9 August 1941.

By 20 October the Germans had reached the western edge of Kharkov, it was taken by 24 October. At that time, however, most of Kharkiv's industrial equipment had been evacuated or rendered useless by the Soviet authorities.

Although the Red Army was preparing for strategic counter-offensives before the war, Barbarossa forced the Soviet supreme command to adopt a strategic defense.

By October Axis operational objectives in Ukraine and the Baltic region were achieved, with only the sieges of Leningrad and Sevastopol continuing.

The Siege of Sevastopol also known as the Defense of Sevastopol, was a military battle that took place on the Eastern Front of the Second World War. On 4 July 1942, the remaining Soviet forces surrendered and the Germans seized the port.

A major offensive against Moscow was renewed; after two months of fierce battles in increasingly harsh weather, the German army almost reached the outer suburbs of Moscow, where the exhausted troops were forced to suspend their offensive. The Battle took place between October 1941 and January 1942, the Soviet defensive effort frustrated Hitler's attack on Moscow, resulting ending of Operation Barbarossa.

By November 1941, Commonwealth forces had launched a counter-offensive, Operation Crusader, in North Africa, and reclaimed all the gains the Germans and Italians had made. The Operation lasted from 18 November to 30 December 1941.

The American counter-proposal of 26 November required that Japan evacuate all of China without conditions and conclude non-aggression pacts with all Pacific powers. That meant Japan was essentially forced to choose between abandoning its ambitions in China, or seizing the natural resources it needed in the Dutch East Indies by force; the Japanese military did not consider the former an option, and many officers considered the oil embargo an unspoken declaration of war.

Newly created Soviet units near Moscow now numbered over 500,000 men, and on 5 December, they launched a massive counterattack as part of the Soviet winter counteroffensive.

On 7 December 1941 (8 December in Asian time zones), Japan attacked Pearl Harbor. The attack on Pearl Harbor a surprise military strike by the Imperial Navy Air Service upon the United States against naval base at Pearl Harbor.

The Philippines campaign fought 8 December 1941, was the invasion of the Philippines by Imperial Japan and the defense of the islands by United States and Philippine forces, the invasion ended on 8 May 1942.

The Malayan campaign was a military campaign fought by Allied and Axis forces in Malaya, from 8 December 1941 – 31 January 1942, The Japanese had air and naval supremacy from the opening days of the campaign. For the British, Indian, Australian and Malayan forces defending the colony, the campaign was a total disaster, the Japanese occupied Malaya.

The declaration of war by the Empire of Japan on the United States and the British Empire was published on December 8, 1941 (Japan time; December 7 in the United States).

Japan occupied the British Crown colony of Hong Kong. The Hong Kong garrison consisted of British, Indian and Canadian units besides Chinese soldiers and conscripts from both within and outside Hong Kong.

On 8 December 1941 (9 December in Asian time zones), the government of the United Kingdom declared war on the Empire of Japan, following the Japanese attacks the prior day.

The Dutch East Indies campaign of 1941–1942 was the conquest of the Dutch East Indies (present-day Indonesia) by forces from the Empire of Japan. Forces from the Allies attempted unsuccessfully to defend the islands. The East Indies were targeted by the Japanese for their rich oil resources which would become a vital asset during the war.

On December 8, 1941 (9 December in Asian time zones), the United States Congress declared war on the Empire of Japan in response to that country's surprise attack on Pearl Harbor the prior day.

The sinking of Prince of Wales and Repulse was a naval engagement, that took place on 10 December 1941 in the South China Sea off the east coast of the British colony of Malaya (present-day Malaysia), 70 miles (61 nautical miles; 110 kilometres) east of Kuantan, Pahang. The Royal Navy battleship HMS Prince of Wales and battle cruiser HMS Repulse were sunk by land-based bombers and torpedo bombers of the Imperial Japanese Navy.

On 11 December 1941, four days after the Japanese attack on Pearl Harbor and the United States declaration of war against the Japanese Empire, Germany declared war against the United States.

On December 11, 1941, the United States Congress declared war upon Germany, hours after Germany declared war on the United States after the attack on Pearl Harbor by the Empire of Japan.

The Japanese conquest of Burma took place between December 1941 and May 1942, which ended the British rules in Burma.

The third Battle of Changsha (24 December 1941 – 15 January 1942) was a major offensive in China by Imperial Japanese forces following the Japanese attack on the Western Allies. The offensive resulted in failure for the Japanese, as Chinese forces were able to lure them into a trap and encircle them. After suffering heavy casualties, Japanese forces were forced to carry out a general retreat. In January 1942, the only Allied success against Japan was a Chinese victory at Changsha.

In May the Germans defeated Soviet offensives in the Kerch Peninsula. The Battle of the Kerch Peninsula was a World War II battle between Erich von Manstein's German and Romanian 11th Army and the Soviet Crimean Front forces in the Kerch Peninsula. It began on 26 December 1941 with an amphibious landing operation by two Soviet armies intended to break the Siege of Sevastopol. From January through April, the Crimean Front launched repeated offensives against the 11th Army, all of which failed with heavy losses. Superior German artillery firepower was largely responsible for the Soviet debacle. On 8 May 1942, the Axis struck with great force in a major counteroffensive code-named Trappenjagd which concluded by around 19 May 1942 with the liquidation of the Soviet defending forces.

On 1 January 1942, the Allied Big Four (the Soviet Union, China, the United Kingdom and the United States) and 22 smaller or exiled governments issued the Declaration by United Nations.

During 1942, Allied officials debated on the appropriate grand strategy to pursue. All agreed that defeating Germany was the primary objective.

Operation Sledgehammer was a World War II Allied plan for a cross-Channel invasion of Europe, as the first step in helping to reduce pressure on the Soviet Red Army by establishing a Second Front. It was to be executed in 1942 and acted as a contingency alternative to Operation Roundup, the original Allied plan for the invasion of Europe in 1943. The operation was eagerly pressed for by both the United States military and the Soviet Union, but rejected by the British, who felt a landing in France was premature, and hence impractical. This perception was reinforced by the failure of the smaller Dieppe Raid in August 1942. As a result, Sledgehammer was never carried out, and instead the British proposal for an invasion of French North Africa took place in November 1942 under the code name Operation Torch.

The offensive halted on 7 January 1942, after having the German armies pushed back 100–250 km (62–155 mi) from Moscow.

The Battle of Rabaul, also known by the Japanese as Operation R, was fought on the island of New Britain in the Australian Territory of New Guinea, on 23 January and February 1942. It was a strategically significant defeat of Allied forces by Japan.

The fighting in Singapore lasted from 8 to 15 February 1942, after the two months during which Japanese forces had advanced down the Malayan Peninsula.

The Bombing of Darwin, on 19 February 1942 was the largest single attack ever mounted by a foreign power on Australia. On that day, 242 Japanese aircraft, in two separate raids, attacked the town, ships in Darwin's harbor.

Allied navies suffered a disastrous defeat at the hand of the Imperial Japanese Navy, on 27 February 1942, in the battle of the Java Sea.

The Indian Ocean raid was a naval sortie carried out by the Imperial Japanese Navy from 31 March to 10 April 1942. Japanese aircraft carriers under Admiral Chūichi Nagumo struck Allied shipping and naval bases around Ceylon, but failed to locate and destroy the bulk of the British Eastern Fleet.

The Battle of Yenangyaung was fought in Burma, which took place between 11 and 19 April 1942. The battle of Yenaungyaung was fought in the vicinity of Yenangyaung and its oil fields.

The Doolittle Raid, also known as the Tokyo Raid, was an air raid on 18 April 1942 by the United States on the Japanese capital Tokyo and other places on Honshu. It was the first air operation to strike the Japanese archipelago. It demonstrated that the Japanese mainland was vulnerable to American air attack, served as retaliation for the attack on Pearl Harbor. The raid caused negligible material damage to Japan, but it had major psychological effects. In the United States, it raised morale. In Japan, it raised doubt about the ability of military leaders to defend the home islands, but the bombing and strafing of civilians also steeled Japanese resolve to gain retribution, and this was exploited for propaganda purposes.

Japan's next plan, motivated by the earlier Doolittle Raid, was to seize Midway Atoll and lure American carriers into battle to be eliminated. As a diversion, Japan would also send forces to occupy the Aleutian Islands in Alaska.

In early May 1942, Japan initiated operations to capture Port Moresby by amphibious assault and thus sever communications and supply lines between the United States and Australia. The planned invasion was thwarted when an Allied task force, centered on two American fleet carriers, fought Japanese naval forces to a draw in the Battle of the Coral Sea.

Concerns the Japanese might use bases in Vichy-held Madagascar caused the British to invade the island (5 May – 6 November 1942).

The Second Battle of Kharkov or Operation Fredericus was a successful Axis counter-offensive in the region around Kharkov. Operation Fredericus took place from 12 to 28 May 1942. The battle was an overwhelming German victory.

In mid-May, Japan started the Zhejiang-Jiangxi Campaign, which lasted from 15 May to 4 September in China, with the goal of inflicting retribution on the Chinese who aided the surviving American airmen in the Doolittle Raid.

The Battle of Gazala was fought during the Western Desert Campaign, west of the port of Tobruk in Libya, from 26 May to 21 June 1942. As both sides neared exhaustion, the Eighth Army checked the Axis advance at the First Battle of El Alamein. To support the Axis advance into Egypt, the planned attack on Malta (Operation Herkules) was postponed. The British were able to revive Malta as a base for attacks on Axis convoys to Libya, greatly complicating Axis supply difficulties at El Alamein.

The Aleutian Islands campaign was a military campaign conducted by the United States and Japan in the Aleutian Islands, starting on 3 June 1942. A battle to reclaim Attu was launched on 11 May 1943, and completed following a final Japanese banzai charge on May 29. On 15 August 1943, an Allied invasion force landed on Kiska in the wake of a sustained three-week barrage, only to discover that the Japanese had withdrawn from the island on July 29.

In June, Japan put its operations into action, but the Americans, having broken Imperial Japanese Navy in the battle of Midway, which took place between 4 to 7 June 1942.

The Germans launched their main summer offensive against southern Russia in June 1942, to seize the oil fields of the Caucasus and occupy Kuban steppe, while maintaining positions on the northern and central areas of the front. The Germans split Army Group South into two groups: Army Group A advanced to the lower Don River and struck south-east to the Caucasus, while Army Group B headed towards the Volga River. The Soviets decided to make their stand at Stalingrad on the Volga.

The Axis offensive in Libya (Battle of Gazala) forced an Allied retreat deep inside Egypt until Axis forces were stopped at El Alamein (First Battle of El Alamein), which lasted from 1 to 27 July 1942. The British prevented a second advance by the Axis forces into Egypt. Axis positions near El Alamein, only 66 mi (106 km) from Alexandria, were dangerously close to the ports and cities of Egypt, the base facilities of the Commonwealth forces and the Suez Canal.

Operation Pedestal (3 to 15 August), was a British operation to carry supplies to the island of Malta in August 1942.

The Guadalcanal campaign also known as Operation Watchtower, was a military campaign fought between 7 August 1942 and 9 February 1943 on and around the island of Guadalcanal. It was the first major land offensive by Allied forces against the Empire of Japan. The Guadalcanal campaign was a significant strategic Allied combined-arms victory in the Pacific theater.

Operation Jubilee, more commonly referred to as the Dieppe Raid, was an Allied assault on the German-occupied port of Dieppe, France, on 19 August 1942. The main assault lasted less than six hours until strong German defenses and mounting Allied losses forced its commanders to call a retreat.

In the Battle of Stalingrad Germany and Axis forces fought the Soviet Union for control of the city of Stalingrad (now Volgograd) in Southern Russia, the battle took place from 23 August 1942 to 2 February 1943, it is one of the bloodiest battles in the history of warfare. Resulting complete destruction of the German 6th Army. After their defeat at Stalingrad, the German High Command had to withdraw considerable military forces from the Western Front to replace their losses.

In August 1942, the Allies succeeded in repelling a second attack against El Alamein. The Battle of Alam el Halfa took place between 30 August and 5 September, south of El Alamein.

With its capacity for aggressive action greatly diminished as a result of the Midway battle, Japan chose to focus on a belated attempt to capture Port Moresby by an overland campaign in the Territory of Papua. Kokoda Track campaign Begun on 21 July 1942, when Japanese forces landed and established beachheads near Gona and Buna on 21 July 1942. The Japanese advanced to within sight of Port Moresby but withdrew on 26 September. They had outrun their supply line and had been ordered to withdraw in consequence of reverses suffered at Guadalcanal.

The Allies commenced an attack of their own in Egypt, dislodging the Axis forces and beginning a drive west across Libya. The Second Battle of El Alamein took place near the Egyptian railway halt of El Alamein, the battle lasted from 23 October to 11 November 1942.

Second Battle of El Alamein was followed up shortly after by Anglo-American landings (Operation Torch) in French North Africa, which resulted in the region joining the Allies. Operation Torch took place between 8 to 16 November 1942.

Hitler occupied Vichy France in Case Anton, which lasted from 10 to 27 November 1942, although Vichy forces did not resist this violation of the armistice, they managed to scuttle their fleet to prevent its capture by German forces.