In 1917, Lenin and the Bolsheviks seized the Winter Palace after the fall of the Russian monarchy. The Russian Revolution ensured the rise of communism, and in the months that followed the Bolsheviks consolidated their regime. After the constituent elections, in which the SRs polled the most votes, it was clear that the Bolsheviks did not have widespread support within Russia.
Shortly after the Bolsheviks pulled the Russian army out of WWI, with the Treaty of Brest-Litovsk in 1918, a Civil War emerged within Russia. During the period 1918 – 1922, a number of White armies (including Western foreign troops) were assembled to defeat the communist Red army. However, the Whites did not establish an effective coalition; and were gradually defeated by the Reds. Trotsky was influential in organizing the Red Army that was triumphant in the Civil War.
With the Civil War ending in 1922, the Bolsheviks established the USSR. The USSR was the first communist regime, and the Bolshevik Party selected Lenin as Soviet Premier. The USSR absorbed the Ukraine, Baltic states and Belarus. However, Poland remained outside of the USSR after the Treaty of Riga.
After the Civil War grain shortages remained in Russia, and many of its railroads were in ruins. As War Communism had done little to revitalize the Russian economy, Lenin proposed the New Economic Policy (NEP). NEP was an economic policy that introduced a degree of free market reform within the USSR, which did not fit easily with the Bolshevik's ideology. But it was Lenin's policy, and that much ensured that it became Bolshevik policy.
An economic revival followed in the USSR. Grain shortages became surpluses with Russian agriculture restored to prewar levels. Russian industry also expanded as railroads were repaired and restored.
NEP remained the primary economic policy until 1928. By then Lenin had passed away, leaving the Bolsheviks to select a new Communist Party leader. Lenin had stated in this final testament that Stalin should not become Communist Party leader, but by 1924 he held a number of the key positions within the party. Stalin was General Secretary of the Communist Party, and that post provided him with a suitable platform to emerge as party leader. As Lenin had not provided any clear details as to whom the Communist Party leader should be, Stalin emerged as Soviet Premier by 1927.
After the rise of Stalin, the Bolsheviks abandoned NEP and replaced it with the Five Year Plans. These plans made expanding Russia's industry a greater priority. The Five Year Plans enhanced the USSR's industrial production in industries such as coal and iron. The Bolsheviks replaced them with new Five Year Plans in 1932, and heavy industries such as steel further expanded.
During the period the Red army greatly expanded to an extent that it was the largest in the world. Russian industry manufactured tanks in increasing numbers to provide further infantry support. The Soviet air force was also the world's largest by 1938. However, their planes still lagged behind Western models and the German Luftwaffe that had Stuka dive-bombers and Messerschmitt aircraft.
Those planes flew in the Spanish Civil War during 1936. During that period Stalin provided support for the communist Republic groups. The Russians supplied them with planes, tanks and artillery. However, Russian military supplies did not ensure a Republican victory as the Nationalists defeated them.
The Cold War had not begun, but before 1939 the USSR did not establish any notable treaties with the West. Britain and France remained suspicious of the USSR, and Stalin did not attend the 1939 Munich Conference. The Allies abandoned the appeasement policy in 1938, after the occupation of Czechoslovakia; and with Europe on the brink of war Stalin signed the Nazi-Soviet Pact in 1939. To the surprise of Britain and France, Stalin promised Russian neutrality when the German army invaded Poland. A superficial alliance with Germany made it clear that Britain and France could not count on Russian military support after they declared war with Germans.
As such, the USSR sat on the sidelines during 1939 and 1940. After the Red Army invaded Finland, Chamberlain permitted British aid to be dispatched to the Finnish army. Debate lingered within Britain as to whether the Allies should also declare war with the USSR. As their armies were overrun in Norway, Holland and France they did not. Britain could not consider declaring war on the Russians after the fall of their primary ally in Europe. Finland initially halted the Red Army's advances, but their outnumbered army could not defeat them.
In 1941, Russian spies began to filter through details of the planned German invasion of USSR to the Politburo. However, Stalin did not listen to the spies, or the Politburo, once it became clearer that the German army was moving toward the Soviet Union's border. In 1941, the German army crossed the Soviet Union's border; and began to blitz military targets within the USSR.
That was a somewhat bleak period for the USSR as the German army advanced further into Russia. Their army had heavy losses, and the Soviet air force was also decimated as Luftwaffe aircraft took out thousands of planes in the air and on the ground. The Germans occupied a number of cities, and their army closed in on Moscow. The wintertime and a fresh batch of Russian winter troops saved the city. As the German army had little winter supplies to counter such reinforcements they began a retreat from Moscow.
The war had not been won, but the Red Army gradually gained the initiative in the East. The German army retreated from Russia, and then the rest of the USSR by 1944. The Russians had heavy losses, but pressed on into Poland, Romania, the Balkans and eastern Germany.
In 1945, Stalin attended the Yalta and Potsdam Conference. Then the USSR had established a clearer alliance with the West, and Stalin made lukewarm pledges for elections across Eastern Europe during the postwar period. Stalin also promised military support for the Pacific War, which was duly provided in 1945 as the Red Army swept into Manchuria.
By then the Red Army had occupied Berlin. An army that had first defeated Western foreign armies in the Russian Civil War now occupied much of Eastern Europe. As Germany was defeated, the alliance faded as the USSR established communist regimes across the Eastern Bloc.
Churchill stated in a speech, “An Iron Curtain has descended across Europe.” Just a few years after 1945 the West airlifted supplies to West Berlin, and the USA supported the Greek national army in the Greek Civil War with the communists. The USSR was already developing its first nuclear arsenal to bridge the gap with the USA. Consequently, a Cold War between the West and the communist Eastern Bloc had begun.