Basic defensive unit used during South Africa's Great Trek, the armed (and illegal) expansion of the Boers from the Cape Colony into Transorangia, Natal and the Transvaal. Although these areas were devastated by the mfecane, and in fact had been assumed to be empty when the Trek began, the Boer convoys were attacked time after time by the Ndebele and other native groups. For the most part they were able to survive by use of the laager and their guns, against which the Africans could field only infantry forces armed with spears.

The laager was formed by moving a group of wagons into a circle or square. Thorny trees and brush were piled under the wagons to keep attackers out. The defenders could then concentrate gunfire as needed from the protection of the wagons, keeping the attackers well beyond spear range for as long as they needed to.

While the laager was practically invulnerable to a direct attack by the invaded peoples, it was vulnerable to siege even when the trekkers had large stocks of food and ammunition, because the Boers' all-important cattle needed room to graze. However, gun-defended laagers proved extremely effective in the long run. Similar tactics were used in the settlement of the American West (albeit less effectively, due to the Native Americans using completely different attack methods), and the word has come to be commonly used for any kind of fortified encampment.