Brief History of World War II

World War II, also recognized as the Second World War and abbreviated as WWII or WW2, was a worldwide conflict between 1939 and 1945. The major participants committed their entire industrial, economic, and scientific powers behindhand the war effort, distorting the limits between civilian and military resources, in a total war directly engaging more than 100 million troops from more than 30 countries. Germany and Japan were engaged after the Axis defeat, and war crimes courts were held counter to Japanese and German leaders.

The attack of Poland by Nazi Germany, commanded by Adolf Hitler, is extensively seen as the start of World War II. The conflict sustained principally among the European Axis nations and the British Empire later the start of combats in North Africa and East Africa, as well as the fall of France in mid-1940, with the Combat in the Balkans, the airborne Combat of Britain, the Blitz of the UK, and the Combat of the Atlantic. On 22 June 1941, Germany commanded the European Axis powers in an invasion of the Soviet Union, launching the Eastern Front, the world's most significant land battleground. By 1937, Japan, which aspired to rule Asia and the Pacific, had declared War on the Republic of China. Japan experienced setbacks in mainland Asia in 1944 and 1945, while the Allies weakened the Japanese Navy and seized important western Pacific islands.

The emancipation of German-occupied territory and the invasion of Germany by the Western Allies and the Soviet Union culminated in the fall of Berlin to Soviet soldiers, Hitler's suicide, and Germany's unconditional capitulation on 8 May 1945. Confronted with an impending invasion of the Japanese archipelago, the threat of more nuclear bombings, and the Soviet entrance into the War counter to Japan and its attack of Manchuria, Japan proclaimed its aim to surrender on 15 August 1945 and signed the surrender document on 2 September 1945, ensuring the Allies' total victory in Asia. Thus, the political and social structures of the world were altered as a result of World War II.

The German attack of Poland and the United Kingdom and France's announcement of War on Germany two days later is widely considered to have started World War II in Europe on 1 September 1939. Taylor believed that the Sino-Japanese Fight and the War in Europe and its colonies happened simultaneously and that the two wars merged in 1941 to form World War II. The Italian raid of Abyssinia on 3 October 1935 is another expected starting date for World War II. The Clashes of Khalkhin Gol, fought between Japan and Mongolian and Soviet forces from May to September 1939, are considered by British historian Antony Beevor to represent the start of World War II. Others see the Spanish Civil War as the Commencement of World War II or a precursor to it. The exact date of the Conflict's end is likewise a point of contention.

Europe

With the defeat of the Central Powers, including Austria-Hungary, Germany, Bulgaria, and the Ottoman Empire, and the Bolshevik takeover of power in Russia in 1917, which led to the formation of the Soviet Union, World War I profoundly transformed the political landscape of Europe. From 1922 to 1925, the Fascist program commanded by Benito Mussolini seized power in Italy, implementing a nationalist, totalitarian. Class-collaborationist agenda that abolished representative democracy repressed socialist, left-wing, and liberal forces and pursued an aggressive expansionist foreign policy to make Italy a world power and promise the creation of a "New Roman Empire."

Following an unsuccessful attempt to overthrow the German government in 1923, Adolf Hitler was chosen Chancellor of Germany by Paul Von Hindenburg and the Reichstag in 1933. The situation deteriorated in early 1935 when the Saar Basin Territory was officially rejoined with Germany, and Hitler rejected the Treaty of Versailles, escalated his rearmament program, and imposed conscription.

In April 1935, the United Kingdom, France, and Italy formed the Stresa Front to restrain Germany, a significant step toward military globalisation; nevertheless, the Franco-Soviet accord had to go through the League of Nations bureaucracy before taking effect rendering it effectively impotent. Concerned about events in Europe and Asia, the United States approved the Neutrality Act in August of the same year. In March 1936, Hitler broke the Versailles and Locarno Treaties by remilitarising the Rhineland, which he did with little opposition due to the appeasement strategy. As a result, Germany and Italy formed the Rome–Berlin Axis in October 1936.

Asia

In the mid-1920s, China's Kuomintang (KMT) party launched a unification drive against regional warlords, ostensibly uniting the country, but it quickly became entangled in a civil war with former Chinese Communist Party supporters and new regional warlords. In 1931, an increasingly militaristic Japanese Empire created the Mukden Event as a pretext to attack Manchuria and found the puppet state of Manchukuo, which had long desired influence in China as the first step in what its administration considered as the country's claim to control Asia. China requested that the League of Nations intervene to prevent the Japanese invasion of Manchuria.

The Italian Invasion of Ethiopia

The Ethiopian Empire was invaded by the armed forces of the Kingdom of Italy, which launched their attack from Italian Somaliland and Eritrea. The conflict resulted in Ethiopia's military occupation and absorption into the newly formed Italian East African colony. Although Italy and Ethiopia were League members, the League did nothing when the former flagrantly violated Article X of the Covenant. The UK and France backed placing sanctions on Italy due to the invasion, but the restrictions were not completely implemented, and the Italian attack continued. After that, Italy dropped its opposition to Germany's desire to absorb Austria.

Spanish Civil War

When the civil conflict started in Spain, Hitler and Mussolini backed the Nationalist rebels led by General Francisco Franco with military aid. Italy supported the Nationalists more than the Nazis did: Mussolini dispatched more than 70,000-foot troops and 6,000 aviation personnel, and 720 aircraft to Spain. The Soviet Union backed the Spanish Republic's current government.

The Japanese Invasion of China

After provoking the Marco Polo Bridge Incident, which culminated in the Japanese effort to invade all of China, Japan took Peking, the old Chinese imperial capital, in July 1937. The Soviets swiftly signed a non-aggression deal with China, essentially ending China's previous cooperation with Germany. Following Nanking's fall, the Japanese slaughtered tens of thousands of Chinese civilians and unarmed combatants. Nationalist Chinese forces achieved their first significant success at Taierzhuang in March 1938, but the Japanese took the city of Xuzhou in May. Chinese forces slowed the Japanese advance by flooding the Yellow River in June 1938.

Soviet–Japanese Border Conflicts

Japanese soldiers in Manchukuo had periodic border conflicts with the Soviet Union and Mongolia in the mid-to-late 1930s. In April 1941, the Soviet Union and Japan contracted a Neutrality Pact. However, Japan adopted the Nanshin-on.

European Occupations and Agreements

Shortly after, the United Kingdom and France followed British Prime Minister Neville Chamberlain's appeasement policy and gave this land to Germany in the Munich Agreement, which was negotiated against the Czechoslovak government's wishes exchange for a pledge of no future territorial claims. Soon after, Germany and Italy compelled Czechoslovakia to yield further territory to Hungary, while Poland acquired the Zaolzie area of Czechoslovakia.

Even though the agreement met all of Germany's declared goals, Hitler was enraged that British influence had prevented him from capturing all of Czechoslovakia in one go. Hitler immediately ordered the invasion to begin on 26 August. Still, he decided to postpone it after learning that the United Kingdom had signed a formal mutual assistance deal with Poland and Italy would remain neutral.

Germany imposed demands on Poland in response to British pleas for direct discussions to avoid War, which served as an excuse to exacerbate relations. On 29 August, Hitler ordered that a Polish plenipotentiary flies to Berlin immediately to discuss the handover of Danzig and to hold a referendum in the Polish Corridor for the German minority to vote on independence. The Poles declined to fulfil with German requests. In a tense meeting with British representative Nevile Henderson on August 30–31, Ribbentrop declared that Germany regarded its claims rejected.

War Breaks Out in Europe

Germany attacked Poland on 1 September 1939, after staging multiple false flag border incidents as a pretext for the invasion. The Polish defences at Westerplatte were the target of the first German attack of the War. After Germany failed to comply with the request, Britain and France declared War on Germany on 3 September, followed by Australia, New Zealand, South Africa, and Canada. After reaching a cease-fire with Japan on 17 September 1939, the Soviet Union invaded eastern Poland under the guise that the Polish state had purportedly ceased to exist. The Warsaw garrison surrendered to the Germans on 27 September, and the Polish Army's final substantial operational unit surrendered on 6 October. Significant Soviet military contingents were moved there in October 1939. Finland declined to sign a similar agreement and refused to cede territory to the Soviet Union. In November 1939, the Soviet Union attacked Finland, and the Soviet Union was expelled from the League of Nations. Soviet military victories were limited, but the Finno-Soviet conflict concluded in March 1940 with considerable concessions from Finland. The Soviet Union conquered Estonia, Latvia, Lithuania, and the Romanian areas of Bessarabia, Northern Bukovina, and the Hertsa region in June 1940.

Western Europe

France kept its fleet, which the UK attacked on 3 July to prevent Germany from seizing it. The Luftwaffe launched attacks on shipping and harbours in early July, kicking off the Battle of Britain. After the United Kingdom turned down Hitler's peace offer, the German air superiority campaign began in August. Still, it failed to overcome RAF Fighter Command, forcing the German invasion of Britain to be postponed indefinitely. The Blitz increased the German strategic bombing onslaught, which could not severely damage the British war effort and mostly concluded in May 1941. The German Navy had success against an over-extended Royal Navy, utilising U-boats against British shipping in the Atlantic, using freshly conquered French ports. The sinking of the German battleship named Bismarck by the British Home Fleet on 27 May 1941 was a decisive victory.

In November 1939, the US took steps to aid China and the Western Allies, amending the Neutrality Act to allow the Allies to make "cash and carry" purchases. Following the German invasion of Paris in 1940, the size of the US Navy was dramatically augmented. The United States agreed to sell American destroyers for British bases in September. Until 1941, a massive majority of the American public opposed any direct military engagement in the battle. Roosevelt accused Hitler of plotting world conquest and dismissed any negotiations as futile, asking for the US to convert an arsenal of democracy and advocating Lend-Lease aid programs to aid the British war effort in December 1940. To prepare for a full-scale onslaught against Germany, the United States began strategic planning. The Tripartite Pact legally unified Japan, Italy, and Germany as the Axis powers in September 1940.

Mediterranean

The operation was over in a matter of months, with only minimal geographical adjustments. Germany began planning an invasion of the Balkans to aid Italy, prevent the British from acquiring a presence in the region, pose a threat to Romanian oil fields, and challenge the British Mediterranean dominance.

In December 1940, British Empire forces in Egypt and Italian East Africa launched counter-offensives against Italian forces. The offensives were a resounding success. The Italian Navy also continued considerable losses, with the Royal Navy abolishing three Italian battleships in a carrier attack off the shore of Taranto and neutralising four more at the Battle of Cape Matapan. Following the defeats of the Italians, Germany sent an expeditionary force to North Africa. In late March 1941, Rommel's Afrika Korps started an offensive against the Commonwealth forces, driving them back. Axis forces moved to western Egypt in fewer than a month and besieged the port of Tobruk. Bulgaria and Yugoslavia signed the Tripartite Pact in late March 1941.

Axis Attack on the Soviet Union

The Soviet–Japanese Neutrality Pact was struck in April 1941. The Soviets were concerned about rising tensions with Germany and the Japanese, hoping to take advantage of the European War by conquering resource-rich European holdings in Southeast Asia. On the other hand, the Germans were methodically assembling forces on the Soviet Union's border in preparation for an attack.

The refusal of the United Kingdom to stop the War, Hitler felt, was motivated by the expectation that the Soviet Union and the United States would join the fight against Germany sooner or later. On 31 July 1940, Hitler declared that the Soviet Union must be destroyed and set his sights on Ukraine, the Baltic nations, and Belorussia. Other prominent German leaders, such as Ribbentrop, saw the Tripartite Pact as an opportunity to form an anti-British bloc by encouraging the Soviet Union to join. Negotiations to see if the Soviet Union would join the accord began in November 1940. Yet, by mid of August, the German Military High Command had decided to stop the invasion of an Military Group Centre that had been harshly exhausted and move the 2nd Panzer Group to strengthen militaries pushing into central Ukraine and Leningrad. The Kiev attack was a booming achievement, encircling and eliminating four Soviet armies and paving the way for subsequent advances into Crimea and industrialised Eastern Ukraine (the First Battle of Kharkov).

Three-quarters of the Axis soldiers and most of their air forces were diverted from France and the central Mediterranean to the Eastern Front, forcing the United Kingdom to rethink its grand plan. In July, the Soviet Union and the United Kingdom forged a military alliance against Germany. In August, the United States and the United Kingdom jointly issued the Atlantic Charter, outlining British and American postwar aspirations. The British and Soviets invaded neutral Iran in late August to safeguard the Persian Corridor and Iran's oil fields and thwart potential Axis advances via Iran into the Baku oil deposits or British India. By October, the Axis had completed its operational goals in Ukraine and the Baltic region, with only the sieges of Leningrad and Sevastopol remaining. The onslaught against Moscow has been relaunched.

Conflict Breaks Out in the Pacific

In 1939, the United States informed Japan that it would not be extending its trade treaty, prompting a series of economic sanctions known as the Export Control Acts, which prohibited the export of chemicals, minerals, and military parts to Japan and increased financial pressure on the Japanese regime. Japan launched its first offensive against Changsha, a strategically significant Chinese city, in September 1939 but was repulsed by the end of the month. The battle among China and Japan had stalemated by 1940, despite multiple offensives on both sides. During these talks, Japan put forward several recommendations that the Americans considered insufficient. At the same time, the US, the UK, and the Netherlands were holding secret talks about defending their territories in the case of a Japanese attack on one of them. Roosevelt bolstered the Philippines, an American region set to earn independence in 1946, and warned Japan that any attacks on neighbouring countries would be met with retaliation from the US.

Japan readied for War, frustrated by the lack of progress and feeling the sting of American–British–Dutch sanctions. The Japanese would thus be free to exploit Southeast Asia's resources while wearing out the overworked Allies in a defensive struggle. Moreover, to prevent American participation while guarding the perimeter, the United States Pacific Fleet and American military presence in the Philippines were to be neutralised from the start. Accordingly, Japan attacked British and American territory with near-simultaneous offensives against Southeast Asia and the Central Pacific on 7 December 1941. Attacks on American warships at Pearl Harbor and the Philippines, Guam, Wake Island, Thailand, Malaya, and the Combat of Hong Kong were between them.

The invasion of Thailand prompted Thailand to declare allegiance to Japan. Other Japanese attacks prompted the US, UK, China, Australia, and some other countries to declare War on Japan formally. In contrast, the Soviet Union, heavily involved in large-scale hostilities with European Axis countries, maintained its neutrality agreement with Japan. However, in solidarity with Japan, Germany and the other Axis governments declared War on the United States, citing the American strikes on German warships that Roosevelt had authorised.

Axis Advance Stalls

The Allied Big Four, the Soviet Union, China, the United Kingdom, and the United States, as well as 22 minor or exiled nations, signed the United Nations Declaration on 1 January 1942, reaffirming the Atlantic Charter and agreeing not to form a separate peace with the Axis forces.

Allied authorities disputed the best broad strategy to follow throughout 1942. Finally, the British and Americans agreed to press their Mediterranean initiative by invading Sicily to control the Mediterranean supply lanes. Although the British advocated for more operations in the Balkans to get Turkey into the War, the Americans obtained a British commitment in May 1943 to confine Allied operations in the Mediterranean to an assault of the Italian mainland and a 1944 invasion of France.

Allies Gain Momentum

The Soviet victory at Kursk signalled the end of German hegemony on the Eastern Front, giving the Soviet Union the upper hand. The Germans sought to hold their eastern front together with the hurriedly built Panther–Wotan line, but the Soviets broke through at Smolensk and the Lower Dnieper Offensive.

Following an armistice with the Allies, the Western Allies invaded the Italian mainland on 3 September 1943. Germany responded by disarming Italian forces that were operating without superior commands in many places, gaining military control of Italian territory, and erecting a series of defensive lines with the support of fascists. Mussolini was then rescued by German special forces, who quickly formed the Italian Social Republic as a new client state in German-occupied Italy, sparking an Italian civil war. In Cairo, Roosevelt and Winston Churchill met with Chiang Kai-shek and later in Tehran, with Joseph Stalin. The former conference decided on the postwar restitution of Japanese territory and military strategy for the Burma campaign. At the same time, the latter agreed on the invasion of Europe by the Western Allies in 1944 and the Soviet Union declaring War on Japan within three months of Germany's collapse.

During the seven-week Battle of Changde in November 1943, the Chinese pushed Japan to fight a costly war of attrition while waiting for Allied assistance. Instead, the Allies launched a series of attacks in Italy in January 1944 against the Monte Cassino line, attempting to outflank it with landings at Anzio.

On 27 January 1944, Soviet troops began a stable operation to drive German forces out of the Leningrad region, ending the world's worst siege. The German Army Group North, assisted by Estonians wishing to re-establish national independence, halted the Soviet onslaught on the pre-war Estonian border. The first of two invasions, an assault against British fortifications in Assam, India, was initiated in March 1944, and Commonwealth positions at Imphal and Kohima were quickly besieged. British forces launched a counter-offensive in May 1944, driving Japanese troops back to Burma by July, and Chinese soldiers surrounded Japanese troops in Myitkyina after invading northern Burma in late 1943. The goal of the second Japanese invasion of China was to eliminate China's primary fighting troops, secure railways connecting the Japanese-held area, and take Allied airfields. By June, the Japanese had taken control of Henan Province and had launched a second offensive on Changsha.

Allies Close In

The Soviet Red Army remained in the Praga district on the other side of the Vistula, idly watching as the Germans put down the Armia Krajowa-led Warsaw Uprising. The Germans also put down a national revolt in Slovakia. Finally, the strategic offensive of the Soviet Red Army in eastern Romania cut off and destroyed the substantial German forces stationed there, triggering a successful coup d'état in Romania and Bulgaria, followed by a movement of those countries to the Allied side.

In September 1944, Soviet soldiers moved into Yugoslavia, forcing German Army Groups E and F to withdraw quickly from Greece, Albania, and Yugoslavia to avoid being cut off. By this time, the Communist-led Partisans, led by Marshal Josip Broz Tito, had taken control of much of Yugoslavia and were delaying German forces further south, having fought an increasingly successful guerrilla campaign against the occupation since 1941. The Soviets started a significant assault on German-occupied Hungary a few days later, which continued until the fall of Budapest in February 1945. Unlike the tremendous Soviet successes in the Balkans, fierce Finnish opposition to the Soviet onslaught in the Karelian Isthmus prevented the Soviets from occupying Finland and resulted in a comparatively mild Soviet-Finnish armistice, despite Finland being obliged to battle their old ally Germany.

By the beginning of July 1944, Commonwealth forces in Southeast Asia had pushed the Japanese back to the Chindwin River while the Chinese had taken Myitkyina. Mount Song was recaptured by Chinese soldiers in September 1944, reopening the Burma Road. The Japanese had more success in China, eventually capturing Changsha in mid-June and Hengyang in early August. They invaded Guangxi province soon after, winning critical battles against Chinese forces at Guilin and Liuzhou by the end of November and successfully uniting their forces in China and Indochina by mid-December. US soldiers in the Pacific continued to push back the Japanese perimeter.

Axis Collapse, Allied Victory

On 16 December 1944, Germany made one final attempt on the Western Front by initiating a massive counter-offensive in the Ardennes and along the French-German border to split the Western Allies, encircle large portions of their troops, and capture their primary supply port at Antwerp to force a political settlement. The operation had been defeated by January, with no strategic objectives met. The Western Allies were stalemated at the German defensive line in Italy. On April 28, Benito Mussolini was assassinated by Italian partisans. Hitler committed himself two days later in besieged Berlin and was succeeded by Grand Admiral Karl Dönitz. On the 7th and 8th of May, total and unconditional surrender in Europe was signed, with the agreement to take effect by the end of the 8th. Until 11 May, the German Army Group Centre held out in Prague.

In the Pacific theatre, American forces, aided by Philippine Commonwealth forces, moved through the Philippines, conquering Leyte by the end of April 1945. They reaffirmed previous agreements regarding Germany, and the US, UK, and Chinese governments underlined their demand for Japan's unconditional surrender, mainly saying that the alternative for Japan is immediate and utter destruction. The United Kingdom held its general election during this conference, and Clement Attlee succeeded Churchill as Prime Minister.

The Japanese leadership rejected the proposal for unconditional surrender, believing that it would negotiate more favourable surrender conditions. Instead, the United States detonated atomic bombs on the Japanese cities of Hiroshima and Nagasaki in early August. Between both the two bombings, the Soviets invaded Japanese-held Manchuria, defeating the Kwantung Army, Japan's main fighting force, following the Yalta Accord. These two incidents prompted Imperial Army leaders who had previously refused to accept capitulation terms to do so. The Red Army also took the Kuril Islands and the southern half of Sakhalin Island.

The Soviet Union also absorbed north-east Romania, sections of eastern Finland, the three Baltic nations, and the Polish areas east of the Curzon line, from which 2 million Poles were evacuated.

To ensure international peace, the Allies established the United Nations, formally appointed on 24 October 1945. It accepted the Universal Announcement of Human Rights as a uniform norm for all member nations in 1948. The War's winners, France, China, the United Kingdom, the Soviet Union, and the United States, became permanent United Nations Security Council members. Although there have been two seat changes, the Republic of China and the People's Republic of China in 1971, and the Soviet Union and its successor state, the Russian Federation, following the fall of the Soviet Union in 1991, the five permanent members have remained the same. The United States became significantly wealthier than any other country, resulting in a baby boom. By the 1950, its gross domestic product per person had surpassed all other powers, and it controlled the global economy. In 1945–1948, the United Kingdom and the United States undertook an industrial disarmament campaign in Western Germany. This resulted in European economic stagnation and a several-year delay in recovery due to international trade interdependencies.

Recovery began in mid-1948 with a currency reform in Western Germany and was accelerated by the Marshall Plan's (1948–1951) direct and indirect liberalisation of European economic policy. As a result, the German economic miracle has been dubbed the post-1948 West German rebound. The Italian economy grew as well, while the French economy recovered. The United Kingdom, on the other hand, was in dire financial straits, and despite receiving a quarter of all Marshall Plan funds, more than any other European country, it remained in a condition of relative economic decline for decades. Despite massive human and material losses, the Soviet Union enjoyed remarkable growth in production in the immediate postwar period. Unfortunately, Japan did not fully recover until much later. By 1952, China had restored to pre-war industrial production levels.

Casualties and War Crimes

Because many deaths went unrecorded, estimates for the total number of casualties in the War vary. Most estimates put the War's death toll at 60 million people, including 20 million military members and 40 million civilians. In addition, deliberate genocide, massacres, mass bombardment, disease, and malnutrition claimed the lives of many civilians. The Soviet Union alone lost about 27 million people during the conflict, including 8.7 million soldiers and 19 million civilians. A fifth of the Soviet Union's population was injured or killed. Germany suffered 5.3 million military casualties, the majority of which occurred on the Eastern Front and during the final engagements in the country.

Hitler's racial tactics killed an estimated 11 to 17 million citizens, including about 6 million Jews, homosexuals, Roma, at least 1.9 million ethnic Poles, and millions of other Slavs, including Russians, Ukrainians, and Belarusians, as well as other ethnic and minority groups. For example, between 1941 and 1945, the Axis-aligned Croatian Ustae harassed and murdered more than 200,000 ethnic Serbs, gipsies, and Jews in Yugoslavia. Simultaneously, Serb nationalist Chetniks persecuted and massacred Muslims and Croats, killing an estimated 50,000-68,000 people, 41,000 of whom were civilians. In addition, between 1943 and 1945, the Ukrainian Insurgent Army slaughtered around 100,000 Poles in the Volhynia atrocities. At the same period, the Polish Home Army and other Polish groups killed 10,000–15,000 Ukrainians in retaliatory strikes.

The Japanese occupation troops killed between 3 million and more than 10 million civilians in Asia and the Pacific, most of whom were Chinese (estimated at 7.5 million). In the Nanking Massacre, fifty to three hundred thousand Chinese citizens were raped and slaughtered, is the most well-known Japanese atrocity. In addition, 2.7 million people died during the Sankō Sakusen, according to Mitsuyoshi Himeta.

Genocide, Concentration Camps, and Slave Labour

Under Adolf Hitler's dictatorship, Nazi Germany was accountable for the Holocaust, which murdered nearly 6 million Jews as well as 2.7 million ethnic Poles and 4 million others deemed unworthy of life, such as the incapacitated and psychologically ill, Soviet convicts of War, homosexuals, Romani, Freemasons, and Jehovah's Witnesses, as part of a deliberate extermination program, effectively turning the country into a genocidal state. Soviet POWs were held in particularly deplorable conditions, and 3.6 million of the 5.7 million Soviet POWs died in Nazi camps. In addition to concentration camps, Nazi Germany established death camps to exterminate individuals on a large scale. In addition, approximately 12 million Europeans from occupied nations were kidnapped and forced to labour as slaves in German industry, agriculture, and the war economy.

During the years 1942–43, the Soviet Gulag became a de facto system of death camps as a result of wartime suffering and malnutrition, which resulted in the deaths of many inmates, including foreign inhabitants of Poland and other nations conquered by the Soviet Union in 1939–40, as well as Axis POWs. Most Soviet POWs released from Nazi camps and many returning civilians were kept in special filtration camps where the NKVD evaluated them, and 226,127 were transferred to the Gulag as accurate or suspected Nazi collaborators after the War. The death rate in Japanese prisoner-of-war camps, many employed as labour camps, was extremely high.

Occupation

This figure excludes the large-scale looting of industrial products, military hardware, raw resources, and other items. As a result, income from occupied countries accounted for more than 40% of Germany's tax revenue, a proportion that grew to about 40% of total German income as the War progressed.

The projected gains of Lebensraum in the East were never realised because of shifting front lines and Soviet scorched earth measures, which denied the German invaders resources. Moreover, unlike in the West, Nazi racial doctrine advocated great brutality towards "inferior people" of Slavic heritage; as a result, most German advances were followed by mass murders. Despite the formation of resistance groups in most occupied countries, German operations in the East and West were not seriously hampered until late 1943.

In Asia, Japan referred to occupied countries as part of the Greater East Asia Co-Prosperity Sphere, which was effectively a Japanese hegemony that it claimed was for the liberation of colonised peoples. Even though Japanese forces were occasionally greeted as liberators from European dominance, local public opinion frequently turned against them due to their war crimes. Japan captured 4,000,000 barrels (640,000 m3) of oil (550,000 tonnes) left behind by retreating Allied forces during its initial invasion.

Home Fronts and Production

If Japanese colonies are included, this is decreased to three times the population and only a 38 percent greater GDP. During WWII, the US manufactured over two-thirds of Allied armaments, including battleships, transports, artillery, aeroplanes, trucks, tanks, and ammo. Though the Allies' population and economic advantages were largely mitigated during the initial rapid blitzkrieg attacks on Germany and Japan, they became the decisive factor by 1942, after the United States and Soviet Union joined the Allies and the War primarily settled into one of attrition, as the Conflict largely settled into one of attrition. While the Allies' capability to out-produce the Axis is frequently attributed to the Allies' greater entree to natural resources, other issues such as Germany and Japan's aversion to employing women in the workforce, Allied strategic bombing, and Germany's late shift to a war economy all played a role.

Advances in Technology and Warfare

In the First World War, the tank was primarily utilised for infantry support to become the principal armament. Tank design was far more advanced in the late 1930s than during World Conflict I, and improvements in speed, armour, and firepower continued throughout the War. Most commanders believed that enemy tanks should be faced with tanks with more impressive specifications at the start of the War. The poor effectiveness of the comparatively small early tank guns against armour and German doctrine avoiding tank-versus-tank combat cast doubt on this theory. This, along with the deployment of combined arms, was a significant component of Germany's very successful blitzkrieg tactics in Poland and France. Tanks were destroyed using various methods, including indirect artillery, towed and self-propelled anti-tank guns, mines, short-range infantry anti-tank weapons, and other tanks. Despite large-scale mechanisation, infantry remained the backbone of all forces, and most soldiers were armed similarly to those in World War I. The portable machine gun spread, with the German MG34 being a famous example, and other submachine guns suitable to close combat in urban and jungle environments. The assault rifle, a late-war creation that combined the rifle and the submachine gun elements, became the standard infantry weapon for most armed forces after WWII.

Most significant belligerents devised ciphering devices to address the challenges of complexity and security associated with employing massive codebooks for cryptography, the most well-known of which was the German Enigma machine. However, the development of SIGINT (signals intelligence) and cryptanalysis allowed decryption to be countered. The Allied deciphering of Japanese naval codes and British Ultra, a pioneering method for decoding Enigma based on information provided to the UK by the Polish Cipher Bureau, which had been decoding early versions of Enigma before the War, are two notable examples. The deception was another type of military intelligence that the Allies utilised to significant effects, such as in operations Mincemeat and Bodyguard.

Other technical and industrial achievements throughout or as a result of the Conflict comprise the world's first programmable computers (Colossus, Z3, and ENIAC), guided artilleries and modern rockets, the Manhattan Project's nuclear weapons development, operations research, and the development of artificial harbours and oil pipelines under the English Channel. During World War II, penicillin was mass-produced and utilised for the first time.