Date: 29 August 1848
The Voortrekkers under Commandant Andries Pretorius were defeated during the Battle of Boomplaats near Trompsburg by the British under Cape Governor-General Harry Smith. The defeat forced the Voortrekkers to flee north of the Vaal River and into the Transvaal.
The Battle of Boomplaats was a direct result of the personal and impulsive action of Sir Harry Smith, who, on 3 February 1848, declared the district between the Orange and the Vaal rivers, the Orange River Sovereignty. The White burghers of the area had hard feelings about this declaration and they called on Commandant-General Andries Pretorius to assist them to regain their independence. In June 1848, Pretorius marched with a thousand men to the Orange River to confront Sir Harry Smith. This commando evicted the British Resident, Major Warden, from his small barracks in Bloemfontein.