The Twentieth Century and After: Wars, Camps, Empires Ending and a Bomb

The empires that fell were the Russian (1917), the German and the Austro-Hungarian (1918) and the Ottoman (the sultanate ended in 1922, the republic in 1923). In the four years of the first world war, some nine to eleven million soldiers died; in the six years of the second, the death toll, soldiers and civilians together, is usually put at 60 to 75 million. Yet in the second half of the century the same world saw the largest sustained rise in living standards in recorded history. A graduate of this course holds both facts without letting either cancel the other.

This piece is long on dates and short on certainty, on purpose. For atrocities it gives the scholarly consensus plainly. For living disputes it describes what each side holds and points to the library's national histories rather than ruling. Its narrative stops in 2022; some later data points are given with their dates, as of 2 November 2026.

1914: the causes, and the argument about them

On 28 June 1914 in Sarajevo, Gavrilo Princip, a young Bosnian Serb in the Young Bosnia movement, shot Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, and his wife Sophie. Six weeks later the great powers of Europe were at war. Step through what happened in between.

Without JavaScript: 28 June assassination; 5–6 July German “blank cheque”; 23 July Austrian ultimatum; 28 July Austria declares war on Serbia; 30–31 July Russian general mobilisation; 1 August Germany declares war on Russia; 3 August on France; 4 August Germany invades Belgium and Britain declares war.

Why did a regional crisis become a continental war? Pick a school; each is given in its own terms.

Without JavaScript: Fritz Fischer blamed Germany's leaders; Christopher Clark described shared responsibility among sleepwalking leaders; structural historians point to alliances, arms races, imperial rivalry and nationalism; Sean McMeekin emphasises Russia's ambitions.

The argument has a legal after-life. Article 231 of the Treaty of Versailles (28 June 1919) made Germany accept responsibility for the losses of the war, which most Germans resented, and which later critics (from John Maynard Keynes in 1919 onward) said set up a future conflict. Others reply that the treaty was less harsh than it was remembered, and that the real failure was in not enforcing it.

Two world wars: total war and its ledger

The first world war (1914–18) mobilised whole economies. Its estimated deaths are 15 to 22 million, of whom nine to eleven million were soldiers. It broke four empires, brought the Russian revolutions of 1917, and left new nations and mandates in the Middle East. It also taught colonised people that the victors' language of self-determination could be used against them: Erez Manela's The Wilsonian Moment (2007) follows the hopes raised in Egypt, India, Korea and China in 1919 and what happened to them in Paris.

The second world war began in China in 1937 (many Chinese historians date it from 1931 in Manchuria), in Europe with Germany's invasion of Poland on 1 September 1939, and became global with Germany's attack on the Soviet Union (22 June 1941) and Pearl Harbor (7 December 1941). It ended in Europe on 8 May 1945 and, after the atomic bombs on Hiroshima (6 August) and Nagasaki (9 August) and the Soviet declaration of war on Japan, with Japan's surrender (announced 15 August, signed 2 September 1945). Historians still argue about what ended the Pacific war: the bombs, the Soviet entry, or both, with Tsuyoshi Hasegawa's Racing the Enemy (2005) emphasising the Soviet declaration and others the bombs.

Without JavaScript: Soviet Union 20–26.6 million; China 14–20 million; Germany 6.9–7.4 million; Poland 5.6–5.8 million; Dutch East Indies 3–4 million; Japan 2.5–3.1 million; India 2.2–3.1 million.

The Holocaust and other genocides: what is established

The word “genocide” was coined in 1944 by the Polish-Jewish lawyer Raphael Lemkin. The UN Genocide Convention (adopted 9 December 1948, in force 12 January 1951) defines it as acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group. Historians use the word more flexibly than courts do, which is one source of dispute; the cases below are the ones where the scholarly or judicial position is clear.

The Holocaust was the murder of about six million Jews (scholarly estimates run from 5.7 to 6.2 million), roughly two thirds of Europe's Jews, by Nazi Germany and its collaborators between 1941 and 1945. It was done by mass shootings across eastern Europe from the invasion of the Soviet Union and in gas chambers at the extermination camps of occupied Poland: Chełmno, Bełżec, Sobibór, Treblinka and Auschwitz-Birkenau, among others. Persecution had come first: the Nuremberg Laws (1935) and the November pogrom of 9–10 November 1938. The Wannsee Conference (20 January 1942) coordinated what was already under way. Auschwitz was liberated by the Red Army on 27 January 1945. The Nazis also murdered at least 250,000 and perhaps about 500,000 Roma (US Holocaust Memorial Museum), disabled people in the “T4” programme, and millions of Soviet prisoners of war and civilians.

The evidence is not in doubt: German orders and reports, the perpetrators' testimony at Nuremberg (1945–46), the Eichmann trial (1961) and the Frankfurt Auschwitz trials (1963–65), the sites, and survivors' accounts. When the British historian David Irving sued Deborah Lipstadt for calling him a denier, the High Court's judgment in April 2000 found that he had distorted the evidence. What historians argue about is how and when the decision came, and why so many people took part. The “intentionalist” view stressed Hitler's plan; the “functionalist” view stressed an escalating, improvised process; most now describe a regime committed to antisemitic goals that radicalised in 1941. Christopher Browning's Ordinary Men (1992) studied one police battalion and argued that peer pressure and careerism mattered; Daniel Goldhagen's reply (1996) argued for a deep German eliminationist antisemitism, and was widely criticised.

Case	When	Estimated deaths	Status
Herero and Nama (German South West Africa)	1904–08	Tens of thousands	Recognised by most scholars; Germany acknowledged it in 2015 and agreed a 2021 development-aid package, while denying legal liability; many Herero and Nama groups rejected the deal
Armenians (Ottoman Empire)	1915–17	600,000 to 1.5 million	Genocide scholars' consensus; the Turkish state rejects the term and describes wartime deportations; many parliaments, and the US government in 2021, recognise it
Jews, Roma and others (Europe)	1941–45	About 6 million Jews	Established
Cambodia (Khmer Rouge)	1975–79	1.2 to 2.2 million deaths	Mass killing is established; the tribunal convicted leaders of genocide against the Vietnamese and Cham minorities (2018–19)
Rwanda (Tutsi)	April–July 1994	About 500,000 to 800,000 (scholars' estimates; the UN often cites about 800,000); the Rwandan government's count is 1,074,017	Established; the UN tribunal's Akayesu judgment (1998) was the first international genocide conviction
Srebrenica (Bosnia)	July 1995	8,372 men and boys	Ruled a genocide by the Yugoslavia tribunal and by the ICJ (2007)

Other cases are contested, as to the word or the facts, between governments, courts and scholars: for example the Soviet famine of 1932–33 in Ukraine, where historians agree on millions of deaths and differ on whether it was aimed at Ukrainians as a group, and recent cases before international courts. This piece does not rule on them. For Ukraine see A Brief History of Russia (32/14) and Ukraine (32/15); for Israel and Palestine see 32/10 and 32/19.

Decolonisation: from 51 states to 193

In 1945 most of Africa, South and Southeast Asia and much of the Caribbean were still ruled from Europe. Within thirty years nearly all of it had become independent. India and Pakistan (14–15 August 1947) were followed by Indonesia (declared 17 August 1945, recognised by the Netherlands in 1949), Ghana (6 March 1957, the first sub-Saharan colony to gain independence), and in 1960 alone 17 new UN members, 16 of them in Africa. Algeria's war (1954–62) ended with independence in July 1962. Portugal's empire ended after its own 1974 revolution, and Namibia became independent in 1990.

Without JavaScript: 51 members in 1945, 99 in 1960, 127 in 1970, 154 in 1980, 159 in 1990, 184 in 1993 and 193 in 2011.

Why then? Historians point to exhausted European states, the example of Japan's early victories over European powers in 1941–42, organised nationalist parties, and an American and Soviet rhetoric hostile to old empires, all pressing on Europe's own unwillingness to pay for fighting. Britain tells a story of planned transfer; critics, among them historians of Kenya's Mau Mau war (1952–60), show repression and violence behind it. The Partition of India in 1947 displaced 12 to 20 million people and killed between 200,000 and two million, a range that shows how hard the counting is. Kwame Nkrumah argued in Neo-Colonialism (1965) that political independence left economic dependence in place, and dependency theorists made the same case; others stress the choices of the new governments. The Organisation of African Unity decided in 1964 to keep the colonial borders, because redrawing them would start wars.

The Cold War: two blocs, one bomb

The Cold War (about 1947–91) was a standoff between the United States and its allies and the Soviet Union and its allies, which never became a direct war between them. It had a few clear points: the Truman Doctrine (March 1947), the Berlin blockade (June 1948 to May 1949), NATO (April 1949), the Soviet atomic test (29 August 1949), the Korean War (1950–53), the Berlin Wall (13 August 1961) and the Cuban missile crisis (16–28 October 1962). It ended with the Soviet Union's dissolution on 26 December 1991.

Historians disagree about its origins. The “orthodox” account blames Soviet expansion; “revisionists” such as William Appleman Williams (1959) stressed American economic aims; “post-revisionists” such as John Lewis Gaddis found a mix. Odd Arne Westad's The Global Cold War (2005) moved the centre to the third world, where the Cold War was hot: Korea, Vietnam, Angola, Afghanistan. The bomb is its signature. Use the slider to see how large the arsenals became.

Without JavaScript: the world total was about 30,900 in 1962, peaked at about 70,400 in 1986, and was about 12,200 in 2026. The United States held about 23,300 and the Soviet Union about 40,200 in 1986.

The Chinese Revolution: from empire to party-state

The Qing dynasty fell in the revolution of 1911 (the Wuchang uprising of 10 October) and the Republic began on 1 January 1912. Warlords and foreign powers divided the country; the Chinese Communist Party was founded in 1921. After the Nationalists turned on their Communist allies in Shanghai in April 1927, the CCP survived the Long March (1934–35) and, in the second Sino-Japanese war, grew among the peasantry. The Communists won the civil war, and Mao Zedong proclaimed the People's Republic on 1 October 1949; the Nationalist government moved to Taiwan. The status of Taiwan is a live dispute: the PRC claims it as a province, and Taiwan's government governs it separately. See A Brief History of China (32/11).

The record has two sides which both belong. Under the PRC, life expectancy in China rose from about 41 in 1949 to about 61 in 1976 (estimates collected by Our World in Data from UN and historical sources), and land reform, literacy and public health expanded. The Great Leap Forward (1958–62) also brought the worst famine in history: estimates of excess deaths range from 15 to 46 million, with newer work (Ashton and Banister, about 30 million; Cao Shuji, 32.5; Yang Jisheng, 36; Chen Yizhi, 43 to 46) clustering between 30 and 46 million. The same life-expectancy series falls to about 33 in 1960. The Cultural Revolution (1966–76) brought mass violence, with estimates of deaths up to one or two million.

After Mao's death in 1976, Deng Xiaoping's reforms (from December 1978) opened the economy. In Maddison data China's income per head rose from about $1,500 in 1973 to about $19,200 in 2022 (2011 international dollars), about thirteen-fold. The Communist Party and its critics, inside and outside China, interpret these decades, including the protests of 1989, differently.

Latin America's century: growth, dictatorship, debt and democracy

Latin American states had been independent for a century when it began. The Mexican Revolution (1910–20) was its first great upheaval. In the 1930s, after the Depression, many governments turned to import-substituting industrialisation, helped by the Argentine economist Raúl Prebisch and the UN's Economic Commission for Latin America (1948): Cárdenas nationalised Mexican oil in 1938, Vargas built Brazil's Estado Novo, and Perón came to power in Argentina in 1946. The Cuban Revolution (1 January 1959) put the Cold War in the Americas.

Then came military rule: Brazil in 1964, Chile on 11 September 1973, Argentina from 1976 to 1983, backed or tolerated at times by the United States. Argentina's official commission in 1984 documented 8,961 disappeared people; human-rights groups give about 30,000. Guatemala's civil war (1960–96) killed about 200,000 people, mostly Maya, according to a UN-backed commission. The debt crisis that began in 1982 ended the “lost decade” of growth, and democracy returned across the region in the 1980s.

Without JavaScript: Argentina was at 57% of the US level in 1900, 49% in 1970 and 31% in 2022. Brazil rose from 11% in 1900 to 25% in 2022; Mexico from 23% to 28%; Chile was 42% in 1900 and 39% in 2022.

Three schools explain the region's growth record. Dependency theorists (Prebisch, Fernando Henrique Cardoso and Enzo Faletto, André Gunder Frank) argued that the structure of world trade kept the periphery poor. Market-oriented economists, including the authors of the “Washington Consensus” (John Williamson, 1989), argued that closed economies and inflation were the cause. Institutionalists such as Stanley Engerman and Kenneth Sokoloff (2000) traced inequality to colonial factor endowments. Argentina, whose income per head in 1913 was above France's and Germany's in these data, is the standing puzzle.

1989, globalisation and the world since 2000

In 1989 communist rule ended across eastern Europe in months: Poland's semi-free election (4 June), Hungary's open border, the fall of the Berlin Wall (9 November), Czechoslovakia's Velvet Revolution, and Romania in December. On the same day as Poland's vote, the Chinese government cleared Tiananmen Square (3–4 June). Germany reunited on 3 October 1990 and the Soviet Union dissolved on 26 December 1991. Why? Gorbachev's reforms, a stagnant economy, national movements and the arms race are all cited; historians disagree about the weights, and about how much credit goes to American pressure. Francis Fukuyama's essay “The End of History?” (1989) said liberal democracy had won; Samuel Huntington's “Clash of Civilizations” (1993) predicted a different pattern.

The next thirty years were an age of integration: China joined the WTO on 11 December 2001, and the financial crisis spread from the United States after Lehman Brothers failed on 15 September 2008. In Maddison data, world income per head roughly doubled between 1990 and 2022 (about $8,200 to $16,700). On the World Bank's $3-a-day line (2021 prices), the share of the world's people in extreme poverty fell from about 43% in 1990 to about 11% in 2022 (World Bank via Our World in Data, 2026); China's growth accounts for much of the drop, and some economists, such as Jason Hickel, argue that the line is too low to measure a decent life.

Since 2000: the attacks of 11 September 2001 and the wars in Afghanistan and Iraq; the Arab uprisings that began in December 2010; the Paris climate agreement (adopted 12 December 2015); the Covid-19 pandemic, which the WHO declared on 11 March 2020 and for which it estimated 14.9 million excess deaths in 2020–21; and the world population passing eight billion on 15 November 2022 (UN). Russia's full-scale invasion of Ukraine began on 24 February 2022; see 32/14 and 32/15 for both countries' histories. Historians are cautious about anything later: archives are closed, memoirs are partial, and what looks decisive often is not. The honest skill is to say what is known, what is claimed, and what is still unknown.

What a graduate just sees

• Causes come in layers: a trigger (Sarajevo), a structure (alliances, arms races) and choices (July 1914), and good historians keep them separate.
• Casualty figures are ranges, and the range itself is a finding.
• The Holocaust is among the best-documented events in history, and denial is not a position in a debate.
• “Genocide” is both a legal and a scholarly word, and they do not always match.
• Decolonisation was the biggest change in the number of states ever, and its borders were mostly inherited.
• The Cold War was cold only in Europe and North America.
• A state can raise life expectancy and cause a famine in the same decade; both facts need explaining.
• Recent history has no settled shape yet; ask who has the sources.

Where it shows up next

• International Relations (35/14): deterrence, alliances and the UN come from this century.
• Public History, Memory & Heritage (35/91): museums, memorials and the law on denial are arguments about these events.
• Comparative Politics (35/13) and Political Economy (35/17): decolonised states, Latin American presidentialism and the post-1989 transitions.
• In the world: why borders in Africa are straight lines, why the Americas and Europe differ on remembering, why great-power politics still turns on nuclear weapons.

If you want to go deeper

• 📘 Textbook. Mark Mazower, Dark Continent (1998), on twentieth-century Europe; Odd Arne Westad, The Global Cold War (2005); and Eric Hobsbawm, The Age of Extremes (1994), a strongly argued survey from a Marxist historian.
• 📘 Gentler. Margaret MacMillan, The War That Ended Peace (2013) and Paris 1919 (2001); Christopher Browning, Ordinary Men (1992).
• 🌐 Free course. MIT OpenCourseWare 21H.009 The World: 1400–Present (Spring 2014), whose later sessions cover the twentieth century.
• 🌐 Free text and data. OpenStax World History, Volume 2; the US Holocaust Memorial Museum Holocaust Encyclopedia; Our World in Data.