It is certainly known that Armenia and Urartu are synonymous. In Darius the Great’s Behistun inscription (ca. 520 BC), the Babylonian toponym “Urashtu” appears as “Armina” in Old Persian and “Harminuia” in Elamite, which correspond to modern “Armenia”. The land is called “Ararat” in Hebrew as well.
The toponym “Urartu” appeared as a regional rather than ethnic description. According to historian Boris Piotrovsky, “the Assyrian name of Uruatri [which gave birth to the Urartu toponym] had no ethnic significance but was most probably a descriptive term (perhaps meaning “the mountainous country”).
While in Old Persian the state was called “Armenia”, in Babylonian records, the name of Urartu (“Urashtu” in Babylonian form, as we mentioned) continued to be used for some time.
With the Assyrian language gradually becoming less used after the decline of Assyria and rise of Media, the toponym “Urartu” was used less and less, until it eventually ceased to exist. The name “Armenia” survived in the annals instead.
According to Herodotus, a decisive role was played by the arrival of a massive Scythian army led by Madyes, the son of Protothyes. Ashur-ubalit, the last Assyrian king, was forced to withdraw to Harran, where he managed to stand until 610 BC. After the fall of Carchemish in 605 BC, the Assyrian kingdom ceased to exist, taking with it the toponym “Urartu”.
For the last time, the name was mentioned in a document of the time of Darius II (ca. 415 BC). In Armenia, the Orontid dynasty has already been established by the time. Thus, undeniably, “Urartu” refers to Armenia. The disappearance of “Urartu” simply marks the disappearance of an exonym, not the state itself. Various other peoples continued to call Armenian with different names.
Hereby, Urartu continued to exist merely known as Armenia after it had ceased to be a Persian satrapy.
Urartu, Urashtu, Ararat, Armenia, and Harminuia used in antiquity have definitely been synonyms. There are no any records of Armenians invading Urartu or some power struggles between Urartu and supposed “Armen” tribes. These events have simply never taken place.
Such a significant geopolitical shift would have surely been noticed and recorded. But because there are no such accounts, we can confidently say that “Armenia” and “Urartu” refer to the same state, as could be seen from the aforementioned records.
2) Potts D. T. (2012), A Companion to the Archaeology of the Ancient Near East
3) The Ancient Civilization of Urartu, translated from Russian by James Hogarth (N.Y., 1969)
4) John Boardman, I. E. S. Edwards, N. G. L. Hammond , E. Sollberger (1982),The Cambridge Ancient History, Vol. 3, Part 1: The Prehistory of the Balkans, and the Middle East