Following Ngqika’s defeat at Debe Nek in 1818, he asked the Cape for help. Subsequently, colonial forces invaded Xhosa territory in December 1818 and triumphed over Ndlambe’s warriors. When they left, however, Ndlambe was again able to defeat Ngqika and then continued into the Colony and attacked Grahamstown in April 1819. The attack was repulsed and Cape forces defeated Ndlambe and marched as far as the Kei River.
In October 1819 the Xhosa chiefs were obliged to recognise Ngqika as paramount chief of the Western Xhosas and he and Somerset made a verbal treaty that provided that the whole area between the Fish and the Keiskamma Rivers, except for the Tyume Valley, which remained Xhosa territory, should be a neutral zone closed to both black and white occupation. Behind the Fish River the 1820 Settlers were established in the Zuurveld in an attempt to provide the dense white settlement that alone could make a frontier line viable.