In 1856, Zulu prince Mbuyasi, outnumbered by his brother Cetshwayo's forces, had requested help from Walmsley, which was refused. Dunn was sent instead to negotiate peace terms between the two warring Zulu brothers, which failed. With a small force of Native Police, Dunn supported the Zulu king Mpande's son Mbuyasi in the bloody battle of succession fought between him and the king's oldest son Cetshwayo. On 2 December 1856, at the Battle of Ndondakusuka, Mbuyazi's forces lost and he was killed, forcing Dunn and other white settlers to flee back to Natal. After the battle, Cetshwayo then clashed with two English traders and took 1,000 head of cattle. His involvement in the battle led to resentment towards Dunn by the white settlers of Natal, so on his own account he re-crossed the Tugela to ask the winner, Cetshwayo, to return the cattle that had belonged to the traders. Cetshwayo agreed, and also requested that Dunn become his advisor in matters related to the British. The cattle were returned and he resigned his position in Natal and settled in Zululand in June/July 1857 and was allocated land on the coast of southern Zululand at oNgoya.