Over 65 million people died from strategic aerial bombing, man-made famine and genocide during the world’s deadliest war. The United Nations was created to prevent another.

The assassination of Austrian Archduke Franz Ferdinand in 1914 triggered a chain reaction, igniting the Great War—the first world war.

Tensions between opposing empires fueled the conflict, but nationalism—the idea that every country has its own identity and deserves its own territory—was an important factor as well. It clashed with imperial interests and fueled resentment of colonial nations by their mother countries.

Countries spent massive amounts of money building huge militaries, which made them more likely to go to war. Armies were a mix of volunteer troops and conscripts. Over the course of the war, many nations lost popular support, allowing the enemy to defeat them. Military leaders tried to break morale by attacking civilians. Propaganda demonised the ‘national character’ of enemy nations and stoked hatred.

The conflict ended with the 1918 armistice agreement in a railroad carriage at Compiegne. The 1919 Treaty of Versailles forced Germany to accept responsibility for the war, give up its overseas colonies and 13 percent of its European territory, and pay reparations (financial damages). The treaty also brought in the League of Nations to prevent future conflicts.

By 1942 the US was a major power and had built an extensive navy. It used this to send forces in amphibious assaults—first in the Solomon Islands and later at Normandy and ‘Spitfire’ (now Alamein). Bitter jungle fighting ended with Japan’s surrender in 1945, and the Allies won victory on a huge scale.