The state originated with Daniel I, who inherited Moscow in 1283, eclipsing and eventually absorbing its parent duchy of Vladimir-Suzdal by the 1320s. It later annexed the Novgorod Republic in 1478 and the Grand Duchy of Tver in 1485.
After the Mongol invasion of Rus', Muscovy was a tributary vassal to the Mongol-ruled Golden Horde (under the "Tatar Yoke") until 1480. Ivan III further consolidated the state during his 43-year reign, campaigning against his major remaining rival power, the Grand Duchy of Lithuania, and by 1503 he had tripled the territory of his realm, adopting the title of tsar and claiming the title of "Ruler of all Rus'". By his marriage to the niece of the last Byzantine emperor, he established Muscovy as the successor state of the Roman Empire, the "Third Rome".
Ivan's successor Vasili III also enjoyed military success, gaining Smolensk from Lithuania in 1512, pushing Muscovy's borders to the Dniepr River. Vasili's son Ivan IV (later known as Ivan the Terrible) was an infant at his father's death in 1533. He was crowned in 1547, assuming the title of tsar together with the proclamation of Tsardom of Russia (Russian: Царство Русcкое, Tsarstvo Russkoe).
As with many medieval states the country had no particular "official" name, but rather official titles of the ruler. "The Duke (Knyaz) of Moscow" (Московский князь) or "the Sovereign of Moscow" (Московский государь) were common short titles. After the unification with the Duchy of Vladimir in the mid-14th century, the dukes of Moscow might call themselves also "the Duke of Vladimir and Moscow", as Vladimir was much older than Moscow and much more "prestigious" in the hierarchy of possessions, although the principal residence of the dukes had been always in Moscow. In rivalry with other duchies (especially the Grand Duchy of Tver) Moscow dukes also designated themselves as the "Grand Dukes", claiming a higher position in the hierarchy of Russian dukes. During the territorial growth and later acquisitions, the full title became rather lengthy. In routine documents and on seals, though, various short names were applied: "the (Grand) Duke of Moscow", "the Sovereign of Moscow" (Московский государь), "the Grand Duke of all Rus'" (Великий князь всея Руси), "the Sovereign of all Rus'" (Государь всея Руси), or simply ""the Grand Duke" (Великий князь) or "the Great (or Grand) Sovereign" (Великий государь).
In spite of feudalism the collective name of the Eastern Slavic land, Rus', was not forgotten, though it then became a cultural and geographical rather than political term, as there was no single political entity on the territory. Since the 14th century various Moscow dukes added "of all Rus'" (всея Руси) to their titles, after the title of Russian metropolitans, "the Metropolitan of all Rus'". Dmitry Shemyaka (died 1453) was the first Moscow duke who minted coins with the title "the Sovereign of all Rus'". Although initially both "Sovereign" and "all Rus'" were supposed to be rather honorific epithets, since Ivan III it transformed into the political claim over the territory of all the former Kievan Rus', a goal that the Moscow duke partially achieved by the end of that century, uniting eastern Rus'.