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20th Century
A century of conflict

Introduction | Wars between nations | Civil wars
Cold War and terrorism | Keeping the peace
A new Europe? | Did you know? | Find out more

Wars between nations

In the early part of the century, competition between nation-states for prestige and resources led to conflicts over colonies. These often spilled over into war. Later, wars were caused by nationalist fervour, Cold War ideologies or ethnic hatred.

The following were the most significant wars of the 20th century.

Russo-Japanese War (1904-05)

This was caused by the attempts of rivals Russia and Japan to gain control over Manchuria and Korea. On 8 February 1904, the Japanese navy launched a successful surprise attack on the Russian fleet at Port Arthur. The Japanese then destroyed the rest of the fleet at the battle of Tsushima on 27-28 May 1905. The Russian troops had more luck on land. The Treaty of Portsmouth, which ended the war, restored Manchuria to Chinese rule. The Russian defeats contributed to the Russian Revolution of 1905.

World War I or Great War (1914-18)

This was caused by economic, colonial and naval rivalries between the main European nations. The conflict started when the Austro-Hungarian archduke Franz Ferdinand (who was also the emperor's heir) was assassinated in the Serbian capital Sarajevo on 28 June 1914.

Because most European countries were bound to each other by alliances, when Austria-Hungary attacked Serbia, the latter's ally Russia declared war on Austria-Hungary. The conflict escalated until the full might of the Allied powers – Britain, France, Russia, Serbia, Belgium, Japan, Italy (from 1915), Romania (from 1916) and the United States (from 1917) – fought against the Central powers: Austria-Hungary, Germany, the Ottoman empire and Bulgaria (from 1915).

The war spread right across Europe, into the Middle East and across the Atlantic (via U-boat attacks) and North Sea (in the battle of Jutland). On land, the Western Front was characterised by trench warfare. Battles such as those of the Somme, Verdun and Passchendaele resulted in huge loss of life for little or no gain in territory.

Trenches – new ways to fight war: World War I

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In the end, the Allied blockade of Germany and the entry of US troops into the war resulted in Allied victory on 11 November 1918. In the Treaty of Versailles of 1919, harsh terms were imposed on Germany, and the Austro-Hungarian and Ottoman empires were dismantled.

World War II (1939-45)

This was caused by the severe effect of the Treaty of Versailles on Germany and – led by Adolf Hitler – its ruthless desire to expand its borders. After Hitler invaded Poland on 1 September 1939, Poland's allies Britain and France declared war on Germany, and the conflict gradually spread across Europe. The United States became involved when Japan – an ally of Germany – attacked its fleet at Pearl Harbor on 7 December 1941.

The Allies comprised Britain and the Commonwealth, the Soviet Union (from June 1941), the United States (from December 1941) and the governments-in-exile of several European nations (including France and Poland) overrun by the German army. The Axis consisted of Germany, Italy (from 1940) and Japan (from 1941), supported by Bulgaria, Finland, Hungary and Romania. For the first time, the conflict was truly global, with battles being fought in Europe, north Africa, the Middle East, China and South-east Asia and in and on the Pacific and Atlantic oceans.

Although Germany and Japan were highly successful at first, their ultimate downfall was due primarily to two countries. Germany was defeated by the Soviet Union, whose people fought with astonishing courage despite horrific losses. Japan was defeated by the superior industrial might of the United States, which was also instrumental in bringing the war in Europe to an end by means of the D-Day invasion of 1944.

Siege of Stalingrad: 1942

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Because of Hitler's refusal to surrender, the war against Germany was total and was fought until he committed suicide in the ruins of Berlin on 30 April 1945.

The American atom bomb attacks on two Japanese cities (Hiroshima and Nagasaki) in August 1945 ended the war in the Pacific.

World War II cost more lives than any other in human history: estimates suggest that as many as 20 million soldiers and 35 million civilians were killed. Of the 55 million total dead, 20 million were Soviet, 13.5 million Chinese, 7.3 million German and 5.4 million Polish. During the war, about 6 million Jews were deliberately exterminated by the Nazis (see The Holocaust).

Korean War (1950-53)

In 1945, following the defeat of Japan after World War II, Korea (which the Japanese had occupied) was partitioned along the 38th parallel into a Soviet-occupied North and a United States-occupied South. Both occupying powers withdrew in 1948.

Two years later, Communist North Korea invaded South Korea and captured Seoul. An international army, approved by the United Nations and led by US general Douglas MacArthur, pushed the North Koreans back to the border. At this point, Communist China's leader Mao Zedong warned that if UN troops crossed the 38th parallel, he would help North Korea. When this warning was ignored, Chinese forces invaded and fought United Nations forces until an armistice was negotiated, a process that lasted from 1951 to 1953.

'Stemming the Red flood' – Korea: 1950

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This war was a symptom of the Cold War. Korea remained divided – with both parts still technically at war – for the rest of the 20th century.

Vietnam War (1961-75)

In 1949, within the French colony of Indochina, a new country, Vietnam, was created by merging Annam, Cochin China and Tonkin. After a war of independence, led by Ho Chi Minh, Vietnam became independent in 1954. However, it was divided along the 17th parallel into Communist North Vietnam and the supposedly democratic South Vietnam, which was actually run by a series of corrupt governments.
After the partition, Communists in the south waged a guerrilla war to reunify the country. In 1961, the United States began giving South Vietnam economic and military aid to prevent the spread of Communism during a time of Cold War tensions.

The Americans used an attack by the North Vietnamese on the US destroyer Maddox in the Gulf of Tonkin in 1964 as the excuse to begin bombing the north. It now appears that there actually was no such attack. Nevertheless, under presidents Lyndon B Johnson, more and more US troops were sent to fight for South Vietnam.

The cost of North Vietnam's largely successful Tet offensive in January 1968 and growing opposition to the war in the US both led to the Paris Peace Conference. This eventually reached an agreement in 1973, when US troops withdrew. The South Vietnamese struggled on for another two years, but in 1975, North Vietnamese troops entered the southern capital of Saigon (now Ho Chi Minh City) and reunified the country.

Six-Day War (1967)

This was the most famous of the four wars fought between Israel and Arab nations over the question of whether an independent state of Israel had the right to exist on Palestinian land.

In 1948, the creation of Israel led to immediate invasion by its Arab neighbours. After the United Nations intervened, Jerusalem was partitioned, the West Bank became Jordanian and the Gaza Strip Egyptian. In 1956, as a result of Nasser's decision to nationalise the Suez Canal, Israel invaded Egypt along with Britain and France.

In 1967 in what would become known as the Six-Day War, Israel – provoked by Palestinian terrorism and Egyptian blockades – attacked Egypt, Syria and Jordan and, in a lightning campaign lasting just six days, defeated all three countries. Israeli troops now occupied Sinai, the Gaza Strip, the West Bank and the Golan Heights.

Despite Egyptian attacks in the Yom Kippur War of 1973, Israel retained its gains until the Camp David Agreement of 1979, when it withdrew from Sinai. For the rest of the century, the occupied territories remained under Israeli control and the problem of a Palestinian state continued unresolved.

Gulf War (1990-91)

This was caused by Saddam Hussein's desire for Iraq to annex Kuwait, an oil-rich kingdom that Iraq had claimed in 1961 when it became independent of Britain. To further this claim, Saddam's troops invaded on 9 August 1990, occupied the country and ignored the United Nations' demand to withdraw. In late November, the UN Security Council's Resolution 678 authorised the UN's members to use force against Iraq to get it to leave Kuwait.

The Coalition – 29 countries led by the United States – attacked on 16-17 January 1991, mainly bombing Iraqi targets. On 4 February 1991, the Coalition army began a ground offensive, liberating Kuwait City on 27 February. Saddam agreed to a ceasefire the next day. In April, Iraq agreed to abandon claims on Kuwait, pay reparations and destroy its weapons of mass destruction. But tensions in the region remained high.

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