In World War Two, the Axis Powers were Germany, Japan, and Italy. They fought against the Allied Powers of Britain, France, the United States, and the Soviet Union.

The Potsdam Conference took place in occupied Germany during the waning days of the Second World War. It was attended by all the Allied Powers, although focus tends to go towards President Truman, representing the United States, Josef Stalin, representing the Soviet Union, and Prime Ministers Winston Churchill and later Clement Attlee, representing Great Britain. The Allied Powers met to decide how to punish Germany and how to rebuild the world after the war.

The Triple Entente, entente meaning "friendship" in French, was cemented by the signing of the Anglo-Russian Entente in 1907. The French and Russians had already entered into an alliance in 1894, while the UK and Frace had put an end to centuries of imperial animosity in 1904. In addition to ending competition between the three constituent powers, the alliance that formed on the basis of the agreements provided for military cooperation as well. The Triple Entente also came about as a geo-political counterweight to the power wielded over Central Europe by the Triple Alliance of Germany, Austria-Hungary, and Italy. The web of alliances that spread over most of Europe has long been thought to have been one of the precipitating factors that led to the spread of war across the continent in WWI. 

The Russian Revolution took place in 1917 and witnessed the decline of the longstanding Russian monarchy to be replaced with a communist government. The primary cause for the Russian revolution was the extended suffering of the Russian people during World War One. The Russian Revolution caused Russia to withdraw from World War One and precipitated the rise of the Soviet Union.

Czar Nicholas II was the last monarch of Russia. When the Russian monarchy fell during the Russian Revolution of 1917, Nicholas and his family were executed. Czar Alexander II abolished serfdom and is therefore sometimes known as Alexander the Liberator. Josef Stalin presided over the Soviet war effort during World War Two.

The first leader of the Soviet Union, which began in 1922, was Vladimir Lenin. Lenin was one of the leaders of the Russian Revolution, in which the monarchy was overthrown and replaced with socialism. He would serve as leader of the Soviet Union until his death, when he was replaced by Josef Stalin. Stalin in turn would reign throughout the thirties and forties until his death led to the leadership of Nikita Khrushchev.

In 1919, Woodrow Wilson was awarded the Nobel Peace Prize for his work founding the League of Nations, although the League was hampered by the refusal of Wilson’s Congress to ratify American participation in the it.

In the immediate aftermath of World War One, the Entente powers sought to make Germany responsible for the financial and human costs of the conflict. The Treaty of Versailles essentially placed all blame for the conflict with the German government, insisting that the Germans pay astronomical reparations. This caused hyperinflation in Germany along with the rise of radical and reactionary ideologies (like Nazism). In an attempt to remedy this situation, the Dawes Plan was established to provide a staggered payment plan and a substantial financial loan from the United States.

The League of Nations was an idea proposed by Woodrow Wilson in the aftermath of World War One. It was part of Wilson’s Fourteen Points, which he published with the aim of preventing a large scale international conflict from breaking out in the future.

Despite being the brainchild of American President Woodrow Wilson, the United States never formally entered the League of Nations. This is because Congress did not ratify American membership in the league. In United States law any treaties or foreign-relations decisions taken by the United States President have to be approved by Congress before they can be enacted. Many historians believe that America’s failure to join the League of Nations contributed to its ineffectiveness and swift decline.