Ossewabrandwag is an Afrikaans term meaning 'oxwagon sentinels' or 'oxwagon guard'.
The Ossewabrandwag (OB) was formed by Johannes Frederik Janse 'Hans' van Rensburg in 1938 to formally represent the increasing Afrikaner nationalism inspired by the Great Trek centenary celebrations. Closely related to both DF Malan's Herenigde Nasionale Party (HNP – 'Reunited National Party') and the Afrikaner Broederbond (AB), the OB rapidly evolved from a cultural organisation into a highly motivated, political voice. By 1941 its membership had risen to approximately 350,000.
During the early years of World War II the Ossewabrandwag became more militaristic, creating an extreme right-wing paramilitary sub-group: Stormjaers. The Stormjaers were modeled on the Nazi Sturmabteilung, the 'Storm Division' or 'Brown Shirts'. During World War II the Stormjaers carried out sabotage within South Africa as a protest against Jan Smuts' United Party government, which was supporting the British. OB members were rounded up and placed in detention camps – including the future prime ministers BJ Vorster, who was a Stormjaers 'general', and PW Botha.
By 1941 the Ossewabrandwag was causing political damage to the HNP and DF Malan spoke out against it in public. In 1942 Malan forbid HNP officials from maintaining membership with the OB, and in 1944 he banned membership of the OB for any HNP member.
With the defeat of Germany in 1945 the Ossewabrandwag went underground, whilst its past members rose steadily in prominence in the Apartheid era government.