After the First World War (1914-18) and the economic crises of the 1920s, aggressive nationalism began to emerge in Europe. Keen to reverse the terms of the Treaty of Versailles (1919) and reassert its dominance of Europe, Germany annexed Austria and parts of Czechoslovakia in 1938.
Economic turmoil had also brought about militaristic movements in the Japanese Empire. Seeking influence and resources, Japan launched an invasion of China in 1937.
3 September 1939
The British Empire and France declare war on Germany following its invasion of Poland.
4 September 1939
The British embark on a long and bitter naval campaign against German U-boats threatening shipping in the Atlantic. It will be the longest campaign of the war.
Germany invades France, Belgium and the Low Countries. The British forces deployed to Europe are forced to evacuate from Dunkirk. France surrenders soon after.
Germany attempts to gain air control over the British Isles before invasion. The Luftwaffe are defeated by the Royal Air Force and the invasion is suspended indefinitely.
Germany commences the strategic aerial bombing of British cities.
German commander Erwin Rommel is dispatched to North Africa to support Italian forces facing defeat by the Allies.
The German Army launches an assault to overthrow the recently established pro-Allied government in Yugoslavia and support the stalled Italian invasion of Greece.
Hitler launches a surprise invasion of the Soviet Union, breaking a pact of non-aggression between the two nations.
In July 1941, the Japanese sent troops to South-East Asia. This threatened British interests in the area and prompted the United States and Britain to establish an oil embargo against Japan. In retaliation, the Japanese launched a devastating attack on the US Navy’s Pacific Fleet at Pearl Harbor on 7 December 1941, drawing the United States into the war.
In the days that followed, the Japanese invaded European colonies across eastern Asia, including the British territories of Hong Kong, Malaya, Singapore and Burma. Their aim was to create a fortified perimeter around a self-sufficient Japan, which could then be defended until the Allies tired of the war.
At Singapore, 80,000 Commonwealth troops are taken prisoner in Britain's worst defeat of the war.
The US Navy severely weakens Japanese naval power in the Pacific with a decisive victory at Midway.
The Allies launch a strategic aerial bombing campaign against German cities.
The Unites States earns another significant victory over the Japanese and goes on the offensive in the Pacific.
British and American forces invade Vichy French-held Morocco and Algeria in order to help clear Axis forces from North Africa.
After a series of battles in the desert, the British secure a decisive victory at El Alamein, forcing the Axis into retreat.
The Germans surrender at Stalingrad and the Soviet Red Army begins to push the Germans back towards Berlin.
In May 1943, the Allies secured victory in North Africa. Their armies advanced from east and west, linking up near Tunis and prompting 250,000 German and Italian troops to surrender.
The Allies next set their sights on clearing the Axis powers from Europe. The invasion of Sicily took place in July 1943, leading to the arrest and expulsion of the Italian Fascist leader Benito Mussolini later that month. This victory prompted Italy to surrender. An armistice was signed on 3 September, but fighting in the country continued.
The Allies land in Italy. But the Germans move in to hold up any sustained advance.
Germany loses the initiative on the Eastern Front and is forced into full retreat by the Red Army.
The Allied advance in Italy is held up in a five-month campaign to break the Italian Winter Line and enter Rome.
Bitter jungle fighting finally earns the Allies a decisive victory over the Japanese in Burma.
The Allies launched the amphibious invasion of Europe on 6 June 1944 in Normandy. They also landed in southern France in August. These operations coincided with a huge Red Army offensive in Eastern Europe that dealt a crushing blow to the Germans.
The Allies' airborne attack aimed at securing a crossing of the Rhine is defeated.
Germany's last offensive in the west, a counter-attack in the Ardennes aimed at dividing the advancing Allies, fails.
British forces liberate the concentration camp at Bergen-Belsen.
The Red Army captures the German capital. The Allies meet the Russians at the River Elbe shortly after.
The Allies pushed into western Germany in February 1945. On 25 April, the Red Army entered Berlin. Five days later, Adolf Hitler committed suicide and the Soviets captured the German parliament building, the Reichstag. After another Allied breakthrough in Italy, German forces there surrendered on 2 May.
Victory in Europe was declared for the Allies on 8 May 1945, following Germany’s unconditional surrender. This led to the occupation and division of Germany.
Commonwealth troops continue to force the Japanese back in Burma. At the same time, US forces seize key Japanese-held islands, including Iwo Jima and Okinawa, and attempt to destroy enemy cities and industry through firebombing.
Allied leaders demand unconditional surrender from the Japanese, citing ‘prompt and utter destruction’ if this is not received.
The United States drops atomic weapons on the Japanese cities of Hiroshima and Nagasaki, causing mass destruction and loss of life. The Red Army also invades Japanese territories between the bombings.
The Japanese agree to unconditional surrender on 15 August. Their official surrender document is signed on 2 September 1945, ending the war.
Over 65 million people died during the Second World War. The majority were civilians killed by strategic aerial bombing, man-made famine and genocide.
In 1945, the United Nations was formed 'to save succeeding generations from the scourge of war'. Axis political and military leaders were put on trial and convicted of war crimes.
Although Britain emerged victorious, the economic and political cost of the conflict accelerated the break-up of its Empire in the years that followed.
On the other hand, the economic and military might of the United States and the Soviet Union made them the dominant global powers. However, their opposing visions of a post-war world, combined with the threat of nuclear conflict, created a Cold War of political and military tension that lasted until the 1990s.