The most immediate political effect of WWI was the collapse of four major empires: the Russian, German, Austro-Hungarian, and Ottoman empires. In Russia, military defeat, critical domestic starvation and political instability contributed to the February Revolution, abdication of Tsar Nicholas II in March 1917, and the Bolshevik seizure of power in November. In the Treaty of Brest-Litovsk, signed on 3 March 1918 with Germany, Soviet Russia accepted the loss of around 930,000 square kilometers, over 56 million people, and territories including Finland, Ukraine, Poland, Estonia, Latvia, Lithuania, and much of Belarus. Not only did this remove Russia from the war, it also created a revolutionary communist state that rejected liberal parliamentarianism and challenged the existing European state system. Similarly, Germany’s defeat forced Kaiser Wilhelm II to abdicate on 9 November 1918, replacing the Hohenzollern monarchy with the Weimar Republic. The Austro-Hungarian Empire disintegrated into Austria, Hungary, Czechoslovakia, and the Kingdom of Serbs, Croats and Slovenes, while Poland and Romania expanded. The Ottoman Empire also collapsed, leading first to the harsh Treaty of Sèvres in 1920 and then to the Turkish nationalist victory under Mustafa Kemal Atatürk, after which the Treaty of Lausanne in 1923 laid foundation for the Turkish Republic. Eric Hobsbawm used “age of catastrophe” to describe WWI as a structural rupture that destroyed the nineteenth-century imperial order as the dominant political form in Central and Eastern Europe.
However, the new political order created after WWI was unstable because self-determination was applied inconsistently. The Treaty of Saint-Germain-en-Laye in 1919 confirmed the break-up of Austria-Hungary and forbade Austria from uniting with Germany. The Treaty of Trianon in 1920 reduced Hungary by two-thirds of its former territory and inhabitants, transferring Transylvania to Romania, Slovakia and Ruthenia to Czechoslovakia, Croatia-Slavonia to Yugoslavia, and Burgenland to Austria, creating revisionist resentment in Hungary. In Germany, the Treaty of Versailles stripped Germany of 13 percent of its territory and 10 percent of its population, including Alsace-Lorraine to France, Eupen-Malmédy to Belgium, the Hultschin district to Czechoslovakia, and Poznan and West Prussia to Poland. Danzig became a Free City under League protection, while the Saar was placed under League administration for fifteen years. Germany also lost all overseas colonies, its army was limited to 100,000 men, conscription was banned, the Rhineland was demilitarized, and Article 231 provided the legal justification for war responsibility and reparations. Politically, Versailles weakened German power but also delegitimized the Weimar Republic, since nationalists portrayed it as the regime that had accepted a dictated peace. Thus, WWI created new nation-states but also produced defeated revisionist powers.
By comparison, WWII’s immediate political effect was the defeat and reconstruction of fascist and militarist regimes. Nazi Germany surrendered unconditionally on 8 May 1945 and was divided into four occupation zones controlled by the United States, Britain, France, and the Soviet Union. The Federal Republic of Germany was founded in May 1949 in the western zones, while the German Democratic Republic was created in October 1949 in the Soviet zone, and Berlin was split between East and West, turning Germany into the central political frontier of the Cold War. Japan’s surrender in August 1945 led to occupation under General Douglas MacArthur as Supreme Commander for the Allied Powers. The 1947 Constitution of Japan transformed the emperor from a divine sovereign into “the symbol of the State and of the unity of the people,” while Article 9 renounced war as a sovereign right. Similarly, Italy abandoned fascism, Mussolini fell in 1943, and after the 1946 referendum Italy became a republic. Ian Kershaw emphasizes WWII had a more direct effect in discrediting fascism as a governing ideology.
A further difference was that WWI produced communism as a major political force, whereas WWII accelerated decolonization. The Bolshevik Revolution created the Soviet Union in 1922, while the Communist International (Comintern), founded in 1919, institutionalized Soviet efforts to spread revolution abroad; by late 1919 it had around half a million members outside Russia, and by 1928 it claimed affiliated parties in more than 40 countries, including Germany, France, Italy, and China. As communist parties spread across Europe and Asia, fear of communism also fueled right-wing authoritarian movements in the interwar period. WWI also created the ideological triangle of liberal democracy, communism, and fascism, a rivalry that shaped domestic politics and international relations throughout the interwar period and laid important foundations for the later Cold War. Arno Mayer’s left-revisionist idea of a European ‘Thirty Years’ Crisis’ frames the two wars as linked ideological struggles. WWII, however, weakened European colonial empires. Britain, France, and the Netherlands survived the war but no longer possessed the same political authority over their colonies, because Japan’s conquest of British Malaya, Singapore, Burma, the Dutch East Indies, and French Indochina had shattered the image of European invincibility in Asia. India and Pakistan became independent in 1947; Indonesia declared independence in 1945 and gained Dutch recognition in 1949; Vietnam’s independence declaration in 1945 led to conflict with France; between 1951 and 1965, 30 African territories achieved independence from European colonial rule. Many of these movements drew legitimacy from postwar principles of self-determination and sovereign equality, while the wartime weakening of Britain, France, Belgium, and Italy reduced their ability to maintain colonial control.
Thus, according to John Darwin, whereas WWI applied self-determination mainly to Europe, WWII globalized it.
The two wars also created different international orders. After WWI, the victorious powers attempted to construct a new system of collective security that differed significantly from the balance-of-power diplomacy that had dominated Europe before 1914. The League of Nations was founded as part of the Versailles settlement to promote international cooperation and prevent future wars. In theory, Article 10 protected members’ territorial integrity, while Article 16 treated aggression as a matter for collective sanctions. The Washington Naval Conference of 1921–22 sought to reduce naval rivalry by establishing limits on capital ships among the major powers, particularly the United States, Britain, and Japan. The Locarno Treaties of 1925 appeared to stabilize Germany’s western borders with France and Belgium; the Kellogg-Briand Pact of 1928 went even further by having more than sixty states renounce war as an instrument of national policy. Together, these agreements reflected a major political shift from the pre-1914 era. But the effectiveness of this system varied. During the relatively prosperous and cooperative “Golden Age” of the mid-1920s, collective security achieved several successes. Nevertheless, the system contained serious weaknesses. The United States never joined the League, the League had no independent military force, and unanimity requirements often prevented decisive action. These weaknesses became increasingly apparent after the onset of the Great Depression in 1929. The League failed to stop Japan’s invasion of Manchuria in 1931, Italy’s invasion of Abyssinia in 1935, and Germany’s remilitarization of the Rhineland in 1936. Zara Steiner admits that although the post-WWI order represented an important innovation in international politics by promoting collective security and delegitimizing war, its institutions lacked the power and unity necessary to withstand the pressures of the 1930s.
After WWII, the United Nations represented a more realistic institutional order. The San Francisco Conference of 1945 involved 50 Allied states, and the UN began with 51 founding members. Unlike the League, the UN included the United States and gave five members—the United States, Soviet Union, Britain, France, and China—permanent seats on the Security Council with veto power, recognizing that international security depended on great-power cooperation. More broadly, WWII produced a fundamentally different international political structure: the wartime alliance between the United States and the Soviet Union quickly collapsed into ideological rivalry. The Truman Doctrine of 1947 committed the United States to supporting governments resisting communist expansion, while the Soviet Union consolidated its influence over Eastern Europe. The postwar order was therefore more institutionalized but also more polarized. NATO, founded in 1949, linked the security of Western Europe to the United States through the principle of collective defense under Article 5. In response, the Soviet Union and its allies established the Warsaw Pact in 1955, formalizing the division of Europe into rival blocs. This bipolar structure was a direct political consequence of WWII because the defeat of Germany and Japan left the United States and the Soviet Union as the dominant global powers, creating a power vacuum that neither side was willing to leave uncontested. Furthermore, many newly independent states in Asia and Africa rejected alignment with either bloc. The emergence of the Non-Aligned Movement in 1961 under leaders such as Jawaharlal Nehru, Josip Broz Tito, and Gamal Abdel Nasser, reflected another indirect political effect of WWII: the weakening of European dominance and the rise of newly sovereign states seeking an independent role in international affairs. Therefore, while the UN provided a framework for international cooperation, Odd Arne Westad argue the broader political legacy of WWII was the creation of a bipolar world order whose influence extended far beyond Europe, even as many states attempted to resist or transcend that division.
Economic Effects
The first major economic effect of both wars was the extraordinary direct cost of fighting. In WWI, the Allied Powers’ loss totaled $125 billion, while the Central Powers lost $61 billion. Britain spent $35.3 billion, France $24.3, and the United States $22.6 billion despite entering only in 1917, showing that the war shifted financial power toward America. Germany alone spent $38 billion, more than any individual Allied country, because it fought a prolonged two-front war and tried to maintain mass military production despite blockade and shortages. This expenditure transformed the economic role of the state. Germany’s government spending rose from about 10 percent of GDP before the war to 59 percent during the war, while its economy contracted sharply. WWI was different from most previous wars because it was the first true total war, in which entire societies and economies were mobilized for the war effort. As a result, economic losses were unprecedented, extending far beyond military expenditure to affect virtually every sector of national economies.
WWII intensified this pattern of total mobilization and imposed enormous direct economic losses on the major combatants. The Soviet Union suffered some of the greatest losses, with wartime destruction estimated at around $128 billion, while Germany lost $48 billion. Despite these losses, the United States was the clearest economic winner because its homeland was not destroyed and its industrial production expanded massively. Between 1941 and 1945, the US exported $32.5 billion of goods through Lend-Lease, including aircraft, ships, vehicles, munitions, food, oil, and industrial materials. However, even in the US, wartime growth did not simply mean consumer prosperity, because aircraft, tanks, ships, and ammunition took priority over civilian goods. Britain, by contrast, was economically exhausted even though it avoided invasion. It depended heavily on American aid, lost much of its prewar financial strength, and emerged from WWII no longer able to sustain its old role as the world’s leading creditor. Thus, both wars expanded state-controlled war production, but WWII more clearly confirmed the United States as the dominant capitalist economy.
The second economic impact was physical destruction. France suffered the most direct Allied industrial damage in WWI due to German occupation. France lost about 14 percent of its industrial output early in the war. The occupied zone had previously produced roughly 75 percent of French coal, 81 percent of iron, and 63 percent of steel. On the Eastern Front, physical destruction was geographically wider: at least 237,000 km² of former Russian imperial territory was directly affected by occupation. 2,700 bridges, 51 depots, and over 1,000 km of track were lost in the Russian railway network, while Galicia suffered severe environmental damage: 11,600 hectares of young forest were burnt, and in the Krasiczyn forests near Przemyśl around 40% of the forest sectors were felled or destroyed. Britain was not invaded, but its economy was heavily affected by naval warfare. 2500 British merchant ships, totaling 7 million gross tons of goods was sank during the war, which accounted for about 40% of Britain’s pre-war fleet. Financially, Britain exhausted much of its prewar overseas investments and gold reserves to finance the war effort, spending approximately £9.5 billion on the war and transforming itself from the world’s leading creditor into a major debtor, particularly to the United States.
WWII caused broader and deeper economic destruction because bombing, occupation, mechanized warfare, and scorched-earth retreat damaged entire national systems. In Britain, about 30 percent of homes were destroyed or damaged by bombing. In France, Belgium, and the Netherlands, about 20 percent of homes were destroyed or damaged. The total cost of war damage for France was three times its annual national income in 1939. Germany’s urban economy was also devastated: in 49 major cities, 39 percent of dwelling units were destroyed or seriously damaged. Poland suffered especially severe destruction, with around 30 percent of buildings, 60 percent of schools and public-administration facilities, 30 to 35 percent of agricultural property, and 32 percent of mines, power facilities, and industries damaged or destroyed. The Pacific war produced a similarly systemic destruction. In Japan, due to U.S. Strategic Bombing, 40 percent of the built-up areas of 66 Japanese cities was destroyed, while about 30 percent of Japan’s entire urban population lost their homes and many possessions. Japan’s industrial and transport economy also collapsed: mining and manufacturing output fell to only about 20 percent of the prewar level, while wartime destruction eliminated 80 percent of shipping, 35 percent of industrial machinery, and roughly 25 percent of national wealth. Other Pacific economies were also devastated. In the Philippines, one of the most heavily damaged Allied territories in Asia, GDP in 1945 was close to only 30 percent of its 1940 level. Therefore, unlike WWI, which mainly devastated particular battle zones and industrial regions, WWII created a general reconstruction crisis involving housing, transport, agriculture, fuel, currency, and industrial production at the same time.
A third major economic effect was financial instability after the wars. After WWI, the Versailles settlement created a dangerous triangle of German reparations, Allied war debts, and American loans. In 1921, the Reparations Commission fixed Germany’s bill at 132 billion gold marks. Britain and France wanted German payments partly because they themselves owed large debts to the United States. Britain owed about $4.3 billion by 1919, while France owed about $4.2 billion to Britain and the United States combined. When Germany defaulted in January 1923, France and Belgium occupied the Ruhr, Germany responded with passive resistance, and the government printed money to support workers and cover expenditure. The result was hyperinflation. The exchange rate collapsed from 4.2 marks per dollar in 1914 to 7,600 in 1922 and then to 30 billions of marks per dollar by late 1923. This destroyed savings, disorganized trade, and weakened confidence in the Weimar economy.
Reconstruction after WWI was therefore improvised and fragile. The Dawes Plan of 1924 stabilized Germany by reducing annual reparation payments, arranging a $200 million foreign loan, reorganizing the Reichsbank, and requiring France and Belgium to evacuate the Ruhr. The Young Plan of 1929 reduced the total to 121 billion gold marks and spread payment over 58 years, while also creating the Bank for International Settlements. Yet this system depended heavily on American private lending to Germany. When the Great Depression cut off US credit after 1929, German recovery collapsed and reparations became politically impossible. By contrast, after WWII, reconstruction was more institutionally organized. At Bretton Woods in 1944, 44 countries designed the IMF and the International Bank for Reconstruction and Development, later the World Bank, to stabilize currencies and finance reconstruction. The Marshall Plan, signed through the Economic Cooperation Act in April 1948, provided $13.3 billion over four years to rebuild Western European economies with food, fuel, machinery, raw materials, and investment. In the East, Comecon was created in 1949 under Soviet leadership to organize trade and planning among communist states. Similarly, under the U.S.-led Allied occupation from 1945 to 1952, Japan was rebuilt as a stable capitalist economy. American occupation assistance totaled about $2.2 billion between 1946 and 1952, mostly through GARIOA relief, including food, raw materials, petroleum, transport equipment, and industrial supplies, and promoted land reforms, reducing the proportion of tenant farmers from 43.5 percent in 1947 to 11.8 percent after reform, while owner-operated land rose from 54 percent before reform to 92 percent. The 1949 Dodge Line then stopped inflation by fixing the exchange rate at 360 yen to the dollar. The Korean War reversed the recession by creating large U.S. “special procurements” orders for Japanese goods and services, worth around $2 billion, which stimulated industry and exports. Thus, while WWI reconstruction depended on reparations and loans, WWII reconstruction created rival but more systematic economic blocs.
Finally, both wars expanded the economic responsibilities of the state, but WWII did so more permanently. After WWI, governments had to manage demobilization, unemployment, war pensions, inflation, food shortages, and the conversion of armament industries to peacetime production. However, fiscal crisis and debt limited their ability to create comprehensive welfare systems. After WWII, welfare became central to reconstruction. In Britain, the Beveridge Report of 1942 identified the five giants of Want, Disease, Ignorance, Squalor, and Idleness, and called for “cradle to grave” social security. This led to policies such as the 1944 Education Act, the 1946 National Health Service Act, and the creation of the NHS in 1948. Economically, this showed that postwar governments accepted responsibility not only for military victory but also for employment, health, education, housing, and social insurance.
Social Effects
The most immediate social consequence of WWI was the destruction of manpower. Germany lost about 2.04 million killed, Russia 1.8 million, France 1.39 million, and Britain 0.9 million. The numbers were also concentrated among men of marriageable and working age. Roughly 20 percent of French men aged between 20 and 40 in 1914 were killed; in Britain, among those aged 20–34, the female surplus rose from 463,000 in 1914 to 770,000 in 1921, resulting in a shrunk workforce and a “lost generation” that would repeatedly echo through the demographics for decades to come. WWI’s casualties also had unusually local effects because of the way armies were recruited. In Britain, the “Pals Battalions” encouraged men from the same town to enlist together, which increased morale and recruitment, but meant that casualties could devastate a single community in one day. The Accrington Pals suffered about 85 percent casualties on the first day of the Battle of the Somme in 1916, with entire teenage male population of a town wiped out. Many survivors returned permanently disabled, unable to work, or psychologically damaged by shell shock. Thus, WWI had a heavy impact on demographics. Civilian suffering was also important in WWI. Direct civilian deaths caused by military action included around 500,000 in Russia and 120,000 in Austria-Hungary. One of the most significant civilian tragedies of the war was the Armenian Genocide, carried out by the Ottoman Empire between 1915 and 1917, with estimated between 800,000 and 1.5 million Armenians killed through mass executions, forced marches, and starvation. Around 2 million French and 9.6 million Belgian civilians lived under German occupation, where they suffered from requisitioning, censorship, forced labor, food shortages, restricted movement, and surveillance. Civilians also suffered from submarine warfare, early air raids, and economic blockade. In Germany, the Turnip Winter of 1916–17 caused at least 400,000 civilian deaths linked to hunger. Disease intensified this suffering. The Spanish flu pandemic of 1918–19 killed at least 20 million worldwide, and troop movements, overcrowded camps, censorship, and weakened healthcare infrastructure helped its spread.
By comparison, WWII produced a much larger and more civilian-centered demographic catastrophe. The war caused roughly 60 million deaths, including about 15 million military battle deaths and around 38–45 million civilian deaths. The Soviet Union suffered the heaviest losses, with around 24–27 million dead. Furthermore, the Holocaust involved the murder of approximately six million Jews, alongside five million other victims targeted by Nazi Germany and its collaborators, including Roma, disabled people, prisoners of war, and political opponents. This was distinct from ordinary battle death because it aimed at the destruction of whole communities, families, religious institutions, and cultural traditions. WWII also witnessed the persecution of ethnic minorities outside Europe. In the United States, following the Japanese attack on Pearl Harbor, Executive Order 9066 authorized the forced relocation and internment of approximately 120,000 Japanese Americans, around two-thirds of whom were U.S. citizens. WWII also featured more displacement and refugees. By May 1945, Europe faced one of the largest displacement crises in modern history. Over 40 million people were displaced in Europe in the immediate postwar period, including refugees fleeing armies, Jews and other persecuted groups deported by the Nazis, forced laborers transported to Germany, prisoners of war, concentration-camp survivors, civilians evacuated from bombed cities, and ethnic Germans expelled from Eastern Europe after 1945. The social effect was long-term because many people did not return to their original homes. Borders, communities, and identities were reshaped by forced migration. The Partition of India in 1947, partly made possible by Britain’s postwar imperial weakness, had 14–18 million people crossed the new borders between India and Pakistan, while an estimated 200,000 to 1 million people died in the communal violence that accompanied the migration. Thus, WWII’s social impact was not only death but uprooting.
Both wars also transformed women’s roles, though neither created complete gender equality. WWI required women to enter public and industrial work on an unprecedented scale. In Britain, women served through organizations such as the Women’s Army Auxiliary Corps, Women’s Royal Naval Service, Women’s Royal Air Force, and Women’s Land Army. They worked in munitions, transport, agriculture, hospitals, government departments, and clerical offices. Female employment in Britain rose from about 24 percent in 1914 to 37 percent in 1918; around 200,000 women entered government departments; 500,000 took clerical work in private offices; and women in transport rose from 18,200 to 117,200. In France, female employment rose from 35.5 percent in 1911 to 47 percent in 1918. In Russia, women made up nearly 45 percent of the industrial workforce, while Austria-Hungary had over one million women join war production. These changes helped support women’s enfranchisement: women gained the vote in Russia, Austria, Czechoslovakia, Poland, Canada, and Britain in 1918, Germany in 1919, and the United States in 1920.
However, the transformation of women’s roles after WWI was rather temporary. Women were often paid less than men, and in 1918, five-sixths of British working women were still confined in occupations traditionally considered feminine, especially domestic service, textiles, clerical work, and nursing. By 1920, around two-thirds of British women had left the jobs they had taken during the war, and by 1921 women’s employment in France had returned close to prewar levels. Holly Mayer’s phrase that women were “ineligible for military service but not for service to the military” highlights that women’s labor was essential, but their equality remained limited.
WWII expanded this pattern further and on a larger scale. In the United States, the number of women in paid employment increased from about 12 million in 1940 to over 18 million by 1945, while the female share of the workforce rose from roughly 27 percent to nearly 37 percent. Around 6 million women entered war industries, and by 1944 women made up approximately 36 percent of the civilian labor force, symbolized by the image of “Rosie the Riveter.” In Britain, over 7 million women were employed by 1943, and nearly 90 percent of single women and 80 percent of married women were engaged in war work, either in factories, agriculture, civil defense, or the auxiliary services. In the Soviet Union, roughly 800,000 women served directly in the Red Army as snipers, pilots, anti-aircraft gunners, communications specialists, medics, and partisans. Despite these advances, significant inequalities remained. In the United States, women working in war industries often earned only about 60–65 percent of male wages. After 1945, many governments actively encouraged women to leave wartime jobs so returning servicemen could be re-employed. Therefore, both wars expanded women’s social visibility and economic participation, but wartime necessity did not automatically produce equal status, equal pay, or lasting gender equality.
The two wars also differed in their legal and moral consequences. WWI exposed the vulnerability of civilians but produced only limited legal protection. The League of Nations minority treaties and the International Labor Organization of 1919 reflected concern for minority rights and social justice, but they lacked strong enforcement. Atrocities such as the Armenian genocide and occupation violence did not lead to a permanent system of international criminal justice. WWII, by contrast, produced a much stronger human-rights legacy. The Nuremberg Trials from November 1945 to October 1946 prosecuted Nazi leaders for crimes against peace, war crimes, crimes against humanity, and conspiracy; 19 defendants were found guilty. The Tokyo Trials similarly prosecuted 28 Japanese leaders, and 7, including former Prime Minister Hideki Tojo, were sentenced to death by hanging. The Universal Declaration of Human Rights was adopted on 10 December 1948, and the Genocide Convention was also adopted in 1948. Thus, WWII transformed social suffering into new legal categories, especially genocide and crimes against humanity.
Finally, both wars reshaped cultural memory and psychology. WWI created a culture of mourning, disillusionment, shell shock, and antiwar literature. In Britain alone, around 100,000 war memorials were erected after WWI, while the Tomb of the Unknown Soldier was created in Arlington in 1921. Writers such as Wilfred Owen, Siegfried Sassoon, Henri Barbusse, and Erich Maria Remarque presented war as destructive and dehumanizing. In Germany, the early “Spirit of 1914,” Burgfrieden, and nationalist enthusiasm gave way to bitterness, antisemitism, and claims that the home front had been “poisoned with Marxism” or betrayal in the “stab in the back” myth. WWII memory was more morally complex. The Holocaust, occupation, bombing, forced migration, and collaboration created difficult questions of guilt and responsibility. Germany later developed Vergangenheitsbewältigung, or “coming to terms with the past,” while France, Italy, Austria, and others often preferred myths of widespread resistance. Tony Judt argued that postwar Europe rebuilt itself through both memory and forgetting, because many societies initially avoided confronting collaboration and local participation in persecution.