4 February 1939
The Ossewabrandwag (OB as it came to be known, meaning Oxwagon Sentinal) was founded as an Afrikaans nationalist organisation in Bloemfontein, under leadership of Colonel J.C.C. Laas. The OB was evidence of the surging Afrikaner Nationalism in the centenary year of the Great trek (1938) and the reaction against the coalition between the National Party (NP) and the South African Party (SAP) during 1930s. The movement was strongly republican-minded. When the Second World War (WWII) broke out in 1939, the OB opposed South Africa's involvement on the side of the Allies. They felt that Germany was not an enemy of South Africa, while they still remembered that Britain had invaded the Republics during the Second Anglo-Boer War. In that war Germany had actually supported the Boers morally. In fact, many Afrikaners felt a kinship with the Germans because of blood ties. Laas was succeeded in December 1940 by Dr J.F.J. (Hans) van Rensburg. Besides the OB and associated with it by a common commanding officer in the person of the Commandant-General, a more radical group, the Stormjaers (Storm Troops), developed. They were responsible for acts of sabotage in South Africa during the war. After WWII the OB gradually faded from the political scene, as the majority members realised that the only effective means of achieving the republican ideal would be through the political party system.
References

Potgieter, D.J. et al. (eds) (1970). Standard Encyclopaedia of Southern Africa, Cape Town: NASOU, v. 8, p. 395-6.|Wallis, F. (2000). Nuusdagboek: feite en fratse oor 1000 jaar, Kaapstad: Human & Rousseau.