Governor
George Napier, seeking to cut off the Voortrekkers from the harbour
in Port Natal, sends Captain Smith with 125 men by land to
re-occupy the port, which was evacuated by the British in 1839.

Port
Natal was given by King Shaka Zulu to the British Cape Colony to establish
a trading port. They set up camp at Congella, an old guard-post
of Shaka. The Voortrekkers had successfully defeated Dingane's
army and had established a short-lived republic called Natalia. It was
at Congella that the Voortrekkers were defeated and Natalia was brought
under the jurisdiction of the Cape Colony. Many Voortrekkers began to
migrate from Congella to search for a new settlement were they could
establish their own republic without British interference.

British policy was to prevent the Voortrekkers from having direct access
to the sea. The British feared that a port under the control of the Voortrekkers
would allow them to establish links with the German government and establish
diplomatic relations that would eventually threaten British imperial
ambitions in southern Africa.

Source:

Wallis, F. (2000). Nuusdagboek: feite en fratse oor 1000 jaar, Kaapstad: Human & Rousseau.