Before Rusa's reign had begun, his father, King Sarduri II, had already expanded the kingdom to southeastern Anatolia, and had managed to retake various Anatolian territories from Assyria during a brief period of weakness in the Assyrian Empire.
However, when Rusa I inherited the throne, the Assyrians had regrouped under their new king Tiglath-Pileser III and had rapidly become a formidable foe, once more expanding their empire. The Assyrians repeatedly invaded Urartu, thus forcing Rusa I to spend the early years of his reign fighting the forces of Assyria. The conflict took a heavy toll on Urartu, particularly on its economy. After suffering numerous reverses, Urartu lost the territory it had annexed under Sarduri II to Tiglath-Pileser III, and was forced to pay tribute to Assyria.
After Tiglath-Pileser III's death, Urartu became restive during the reign of Shalmanassar V, but not for long. Sargon II, who came to the throne in 722 BC, continued the Assyrian hostility against Urartu. He declared war on Urartu in 715 BC, thus beginning the Urartu-Assyria War. After defeating the Urartian ally, the Kingdom of Mannea, the Assyrians attacked Urartu. Rusa I was decisively defeated in this war and Urartu was once more subjugated, being forced to pay large annual tributes to Assyria. Rusa I committed suicide after this war.