Final answer:
Ivan IV, also known as Ivan the Terrible, was the first ruler to declare himself Tsar of all the Russias and expanded Russian territory significantly. Peter the Great modernized Russia and created the Russian Empire, while Nicholas II was the last Tsar, his reign ended by the Russian Revolution.
Step-by-step explanation:
Russian Tsars and their Contributions
Among the rulers of Russia mentioned, Ivan IV, known as Ivan the Terrible (r. 1547-1584), was the first to declare himself Tsar of all the Russias, a title echoing the Latin 'Caesar.' He greatly expanded the territory of Russia by annexing the khanates of Kazan, Astrakhan, and Siberia, and encouraged the colonization of Siberia by recruiting Cossacks. Ivan IV was also known for his contribution to Russian architecture, as he was significant in rebuilding the Kremlin in Moscow. His legacy as the Tsar who established a centralized Russian state is one of the reasons he is also referred to as Ivan the Terrible.
In contrast to Ivan IV, it was Peter the Great (r. 1672-1725) who later modernized Russia and formally created the Russian Empire. His reforms were extensive; he travelled to Europe in disguise to learn about shipbuilding and administration. Peter's rule significantly changed the landscape of the Russian state and society, earning him the title of 'Otets Otechvesta' (Father of the Fatherland) and marked Russia's transformation into a major European power.
The last Tsar of Russia was Nicholas II, who reigned from 1894 until the Russian Revolution in 1917. His tenure saw pivotal events including the Russo-Japanese War and World War I, which ultimately contributed to the end of the Romanov dynasty and the rise of the Soviet Union.