Ashur-uballit I reigned over Assyria (1365 - 1330 BC) as it truly gained traction and was completely free of Mittanian control, as shown in his letters found at Amarna. These letters are significant, as up until this point all communications had been through the Mittanni; Ashur-uballit's predecessors were not allowed to directly contact other kingdoms. In an unprecedented move, Ashur-uballit I communicated with Egypt (forming trade links) and gave one of his daughters to the Kassite king in Babylonia (forming a dynastic link).
Ashur-uballit I did not detail his own military campaigns, but his successors note that he thrust his military northwards into mountains that hid disruptive gangs, contained raw materials and held ideal horse-breeding areas. These northern and eastern mountains (along the borders of modern-day Iraq, Syria, Turkey and Iran) are a recurring military theme throughout Assyrian history. Ashur-uballit's great-grandson said that
the security of his kingship was firmly established as far distant as the mountains (north Iraq) and that he succeeded against
the forces of the widespread land of the Subarians (referring to general northerners) and a land called Musri (a vague northwest region).