Eriba-Adad was king of Assyria

Assyria

Assyria was a Semitic Akkadian kingdom, extant as a nation state from the mid–23rd century BC to 608 BC centred on the Upper Tigris river, in northern Mesopotamia , that came to rule regional empires a number of times through history. It was named for its original capital, the ancient city of Assur...

 from 1392 BC to 1366 BC.

He was probably a vassal

Vassal

A vassal or feudatory is a person who has entered into a mutual obligation to a lord or monarch in the context of the feudal system in medieval Europe. The obligations often included military support and mutual protection, in exchange for certain privileges, usually including the grant of land held...

 of Mitanni

Mitanni

Mitanni or Hanigalbat was a loosely organized Hurrian-speaking state in northern Syria and south-east Anatolia from ca. 1500 BC–1300 BC...

. However, this kingdom got tangled up in a dynastic battle between Tushratta

Tushratta

Tushratta was a king of Mitanni at the end of the reign of Amenhotep III and throughout the reign of Akhenaten -- approximately the late 14th century BC. He was the son of Shuttarna II...

 and his brother Artatama II

Artatama II

Artatama II was an usurper to the throne of king Tushratta of Mitanni in the fourteenth century BC. He may have been a brother of Tushratta or belonged to a rival line of the royal house. The Hittite king Suppiluliuma I made a treaty with Artatama following his invasion of Mitanni. His son,...

 and after this his son Shuttarna II

Shuttarna II

Shuttarna II was a king of the Hurrian kingdom of Mitanni in the early 14th century BC.Shuttarna was a descendant and probably a son of the great Mitannian king Artatama I. He was an ally of the Egyptian Pharaoh Amenhotep III and the diplomatic dealings of the kings are briefly recorded in the...

, who called himself king of the Hurri

Hurrians

The Hurrians were a people of the Ancient Near East who lived in Northern Mesopotamia and adjacent regions during the Bronze Age.The largest and most influential Hurrian nation was the kingdom of Mitanni. The population of the Hittite Empire in Anatolia to a large part consisted of Hurrians, and...

, while seeking support from their Assyrian vassals. A pro-Hurri/Assur faction appeared at the royal Mitanni court, which his son and successor Ashur-uballit I

Ashur-uballit I

Ashur-uballit I , was king of the Assyrian empire . His reign marks Assyria's independence from the kingdom of Mitanni, by defeating Shuttarna II; and the beginning of Assyria's emergence as a powerful empire...

 would take advantage of.