The term Cossacks' Leader is a reference to the TSAR, which is a four-letter word. The TSAR was the title of the monarch of the Russian Empire from 1547 to 1917. The TSAR was the absolute ruler of the country and had complete control over the government and the people. The TSAR was also the leader of the Cossacks, a group of people who lived in the southern part of Russia and were known for their military prowess.