In September 1917
The Russian Monacrchy which at the time was led by Czar Nicholas II was overthrown by the Bolshviks who were led by Vladmir Lenin.
Stalin played a key role in the bolshviks revolution, his role was to convert the non russian citizens to become bolshviks supporters.
greece
Iran
The Bolsheviks did not seize power during the Russian Civil War. They had already seized governmental power from the Provisional Government in 1917. The civil war is generally figured to have started in 1918. The Bolsheviks managed to retain their power, not seize it, by winning the civil war.
1976
usurp
To adopt, Seize power, or invade.<(-_-)>
Iran.
A revolt designed to overthrow an existing government and seize power
Usually (but not necessarily) by force. But in any event, not by statutorily legal lines of succession.
the tyrants were able to seize power from the nobles because they had the help and support of the Greek farmers, merchants, and the artisans.