Bit-Zamani had belonged to Assyria by right of conquest ever since the death of Ammibaal; Izalla and Bit-Bakhiani had fulfilled their duties as vassals whenever Assur-nazir-pal had appeared in their neighbourhood; Bit-Adini alone had remained independent, though its strength was more apparent than real. The districts which it included had never been able to form a basis for a powerful state. If by chance some small kingdom arose within it, uniting under one authority the tribes scattered over the burning plain or along the river banks, the first conquering dynasty which sprang up in the neighbourhood would be sure to effect its downfall, and absorb it under its own leadership. As Mitani, saved by its remote position from bondage to Egypt, had not been able to escape from acknowledging the supremacy of the Khati, so Bit-Adini was destined to fall almost without a struggle under the yoke of the Assyrians. It was protected from their advance by the volcanic groups of the Uraa and Tul-Aba, which lay directly in the way of the main road from the marshes of the Khabur to the outskirts of Tul-Barsip. Assur-nazir-pal, who might have worked round this line of natural defence to the north through Nirbu, or to the south through his recently acquired province of Laqi, preferred to approach it in front; he faced the desert, and, in spite of the drought, he invested the strongest citadel of Tul-Aba in the month of June, 877 B.C. The name of the place was Kaprabi, and its inhabitants believed it impregnable, clinging as it did to the mountain-side "like a cloud in the sky."* * The name is commonly interpreted "Great Rock," and divided thus--Kap-rabi. It may also be considered, like Kapridargila or Kapranisha, as being formed of _Kapru_ and _abi_; this latter element appears to exist in the ancient name of Telaba, Thallaba, now Tul-Aba. Kapr-abi might be a fortress of the province of Tul-Aba.