Final answer:
The Treaty of Brest-Litovsk was signed in 1918 and involved Russia giving up significant territories to the Central Powers, mainly Germany. This allowed Lenin and the Bolsheviks to focus on building a Communist state.
Step-by-step explanation:
The Treaty of Brest-Litovsk was a treaty signed on March 3, 1918, between Russia and the Central Powers during World War I. With this treaty, Russia gave up significant territories, including areas of Poland and Ukraine, Finland, and the Baltic states (Lithuania, Latvia, and Estonia), to the Central Powers, mainly Germany. It allowed Lenin and the Bolsheviks to focus on building a Communist state, the Soviet Union.