>In the early 1900s, Russia was one of the most impoverished countries in Europe with an enormous peasantry and a growing minority of poor industrial workers.

>Much of Western Europe viewed Russia as an undeveloped, backwards society. The Russian Empire practiced serfdom—a form of feudalism in which landless peasants were forced to serve the land-owning nobility—well into the nineteenth century. In contrast, the practice had disappeared in most of Western Europe by the end of the Middle Ages.

>In 1861, the Russian Empire finally abolished serfdom. The emancipation of serfs would influence the events leading up to the Russian Revolution by giving peasants more freedom to organize.

In the Battle of Stalingrad (1942–43), the advancing Germans were finally stopped by the Red Army in desperate house-to-house fighting. From The Second World War: Allied Victory (1963), a documentary by Encyclopædia Britannica Educational Corporation.

Along with World War I, World War II was one of the great watersheds of 20th-century geopolitical history. It resulted in the extension of the Soviet Union’s power to nations of eastern Europe, enabled a communist movement to eventually achieve power in China, and marked the decisive shift of power in the world away from the states of western Europe and toward the United States and the Soviet Union.

A gigantic mushroom cloud rising above Hiroshima, Japan, on August 6, 1945, after a U.S. aircraft dropped an atomic bomb on the city, immediately killing more than 70,000 people.

READ MORE ON THIS TOPIC

20th-century international relations: World War II, 1939–45

By the early part of 1939 the Germandictator Adolf Hitler had become determined to invade and occupy Poland. Poland, for its part, had guarantees of French and British military support should it be attacked by Germany. Hitler intended to invade Poland anyway, but first he had to neutralize the possibility that the Soviet Union would resist the invasion of its western neighbour. Secret negotiations led on August 23–24 to the signing of the German-Soviet Nonaggression Pact in Moscow. In a secret protocol of this pact, the Germans and the Soviets agreed that Poland should be divided between them, with the western third of the country going to Germany and the eastern two-thirds being taken over by the U.S.S.R.

Soviet foreign minister Vyacheslav Molotov, having negotiated the German-Soviet Nonaggression Pact of August 1939, is greeted by German foreign minister Joachim von Ribbentrop and other officials in Berlin. From “The Second World War: Prelude to Conflict” (1963), a documentary by Encyclopædia Britannica Educational Corporation.Encyclopædia Britannica, Inc.

Having achieved this cynicalagreement, the other provisions of which stupefied Europe even without divulgence of the secret protocol, Hitler thought that Germany could attack Poland with no danger of Soviet or British intervention and gave orders for the invasion to start on August 26. News of the signing, on August 25, of a formal treaty of mutual assistance between Great Britain and Poland (to supersede a previous though temporary agreement) caused him to postpone the start of hostilities for a few days. He was still determined, however, to ignore the diplomatic efforts of the western powers to restrain him. Finally, at 12:40 PM on August 31, 1939, Hitler ordered hostilities against Poland to start at 4:45 the next morning. The invasion began as ordered. In response, Great Britain and France declared war on Germany on September 3, at 11:00 AMand at 5:00 PM, respectively. World War II had begun.

Overview of the German invasion of Poland (1939), which marked the beginning of World War II.

In September 1939 the Germans overrun Poland, forcing all of Europe into a state of war. From “The Second World War: Prelude to Conflict” (1963), a documentary by Encyclopædia Britannica Educational Corporation.

LOAD MORE

On June 17, 1940, the defeated French signed an armistice and quit World War II. Britain now stood alone against the power of Germany’s military forces, which had conquered most of Western Europe in less than two months. But Prime Minister Winston Churchill rallied his stubborn people and outmaneuvered those politicians who wanted to negotiate with Adolf Hitler. But Britain’s success in continuing the war would very much depend on the RAF Fighter Command’s ability to thwart the Luftwaffe’s efforts to gain air superiority. This then would be the first all-air battle in history.

Hitler’s troops were already wreaking havoc in Poland, having invaded on the first of the month. The Polish army began retreating and regrouping east, near Lvov, in eastern Galicia, attempting to escape relentless German land and air offensives. 

But Polish troops had jumped from the frying pan into the fire—as Soviet troops began occupying eastern Poland. The Ribbentrop-Molotov Non-aggression Pact, signed in August, had eliminated any hope Poland had of a Russian ally in a war against Germany.

Little did Poles know that a secret clause of that pact, the details of which would not become public until 1990, gave the U.S.S.R. the right to mark off for itself a chunk of Poland’s eastern region. The “reason” given was that Russia had to come to the aid of its “blood brothers,” the Ukrainians and Byelorussians, who were trapped in territory that had been illegally annexed by Poland. Now Poland was squeezed from West and East—trapped between two behemoths. Its forces overwhelmed by the mechanized modern German army, Poland had nothing left with which to fight the Soviets.

The Soviet Union would wind up with about three-fifths of Poland and 13 million of its people as a result of the invasion.

Now that the war was over, negotiating and maintaining the peace was the practical responsibility of the new U.N. Security Council, made up of the United States, Great Britain, France, the Soviet Union, and China. Each would have veto power over the other. Winston Churchill called for the United Nations to employ its charter in the service of creating a new, united Europe-united in its opposition to communist expansion-East and West. Given the composition of the Security Council, this would prove easier said than done.