Shaushtatar is the son of Parshatatar.

By the time he ascends the throne at some time in the fifteenth century BCE, his father has installed Hurrian client kings in a number of cities, making it easier for Shaushtatar to make Mittani a Mesopotamian power.

Now freed from the constant threat undergone by Mitanni of the Egyptians, Shaushtatar turns his attention toward Assyria.

In a treaty made more than a century later, Shaushtatar is told to have sacked Assur, the Assyrian capital.

He is reputed to have brought the golden doors of the palace to his own capital of Washshukanni, making vassal states of Assyria and Arrapha.

After his invasion of Assyria, Shaushtatar turns his army westward across the Euphrates, along the way gathering beneath his sway all the northern Syrian states as he brings his army to the Mediterranean coast.

He is looking to extend Mitanni's power further south, perhaps into Palestine.

However, much of southern Syria still lies within the Egyptian sphere of influence, which has long been a threat to Mitanni.