Kongo began working towards a Spanish alliance, especially following António I's succession as king in 1661. Although it is not clear what diplomatic activities he engaged in with Spain itself, the Portuguese clearly believed that he hoped to repeat the Dutch invasion, this time with the assistance of Spain. António sent emissaries to the Dembos region and to Matamba and Mbwila, attempting to form a new anti-Portuguese alliance. The Portuguese had been troubled, moreover, by Kongo support of runaway slaves, who flocked to southern Kongo throughout the 1650s. At the same time, the Portuguese were advancing their own agenda for Mbwila, which they claimed as a vassal. In 1665, both sides invaded Mbwila, and their rival armies met each other at Ulanga, in the valley below Mbanza Mbwila, capital of the district.