Final answer:
Russia signed a peace treaty with Germany, known as the Treaty of Brest-Litovsk, after the Russian Revolution allowed Germany to concentrate on the Western Front and contributed to the US joining the war.
Step-by-step explanation:
As a result of the revolution in Russia, Russia signed a peace treaty with Germany. This treaty, known as the Treaty of Brest-Litovsk, was signed in March 1918. Following the Russian Revolution, the new Bolshevik government under Vladimir Lenin sought to withdraw from World War I to focus on internal issues and establishing a communist state. Germany, eager to eliminate the Eastern Front and concentrate its forces in the West, offered generous terms to the Russians.
This enabled Germany to move its troops and intensify its offensive against France and Britain in Western Europe. The U.S., perceiving the growing threat and wishing to support its allies, joined the war shortly after Russia's withdrawal, helping to tilt the balance towards Allied forces and contribute to the eventual defeat of Germany in November 1918 with the signing of the armistice.