Final answer:
The abdication of Tsar Nicholas II led to the Communist control of Russia.
Step-by-step explanation:
The event that led to the Communist control of Russia was the abdication of Tsar Nicholas II. In 1917, amidst desperate conditions and loss of life in World War I, the Tsar abdicated his throne. The provisional government that was put in place was quickly overthrown by the Bolsheviks, a group of revolutionaries led by Vladimir Lenin, who eventually established a state based on communism.