Barely 12 years after the Treaty of Vereeniging had been signed, and four years after the union of the colonies, the British Empire went to war with Germany and Austria. In terms of the Act of Union, South Africa was automatically involved. Prime Minister Louis Botha had no choice in the matter. Botha informed Britain that South Africa would undertake its own defence to free British troops for engagement elsewhere. London, however, requested Botha to despatch South African troops to capture the German South West ports of Swakopmund and Luderitz Bay as well as the radio transmitting station at Windhoek.
  Botha felt honour bound to accede to the request because Britain had reserved at the time of Union rights to intervene in South African foreign affairs. It was a difficult decision to make but Botha raised a volunteer force for the campaign. Immediately, General Barry Hertzog and Marthinus Theunis Steyn, the former President of the Orange Free State, opposed the dispatch of South African troops to fight beyond the borders of the Union merely to serve the interests of the British Empire. Republican sentiments still ran high after the signing of the Treaty of Vereeniging and many Boer War heroes argued that England's predicament, in fact, was South Africa's opportunity to reinstate a Republic.
  Christiaan Beyers, then Commandant-General of the Union Defence Forces, together with Generals Koos de la Rey and Christiaan de Wet, Major Jan Christoffel Kemp, officer commanding in Potchefstroom, and Lt.-Col. Manie Maritz, who was in charge of the North West Cape district on the German South West border, were all opposed to the use of South African forces beyond the Union's borders, and they chose to rebel.
  The revolt was planned to coincide with Beyers' resignation as Commandant General, and on October 2, 1914 Manie Maritz declared the Union an independent Republic; then he crossed into German South West to seek help against the government of Louis Botha.
  The move brought de Wet, Kemp and Beyers into action and, as of old, Boer commandos were called up ... the strongest response coming from the northern Free State and the Western Transvaal.

  Botha declared martial law on October 12, 1914, and with a heavy heart he called upon his supporters to crush the rebellion. Botha's government troops were mustered and they passed through Vereeniging in motorised columns proceeding south into the Free State to quash the revolt. This time, Vereeniging was not to hear the crack of rifle fire, for the fighting took place further south.
  The revolt was quashed quickly. Kemp fled from Potchefstroom with 600 followers to join Maritz in German South West and Beyers was drowned while attempting to cross the Vaal River near Makwassie to join the Free State rebel force which Botha scattered at Mushroom Valley on November 16. Earlier, General Koos de la Rey was shot dead by mistake when his car passed a road block intended for the notorious Foster Gang.
  De Wet was captured and jailed; and when Maritz and Kemp, with German support, tried to capture Upington, they were defeated. Kemp surrendered and Manie Maritz fled to Angola. The revolt was over and Botha was left free to mount the campaign London had demanded, which was fulfilled with the subsequent occupation of German South-West Africa.
  With the advent of World War I both the collieries and the steelworks were pressed into war production at a time when many Vereeniging men had left on service with the armed forces. The steelworks began to produce castings and steel sections for a South African engineering industry largely robbed of overseas supply. The collieries, in 1915, brought to the surface a record annual production of 500,000 tons of coal.
  In 1917, the Indian Muslim community purchased a site in Main Street, now known as Voortrekker Street, on which a mosque was built, and it is indicative of the town's development that the site then bought for £360 (R720) is today valued at £90,000 (R 180,000) and the mosque at £18,000 (R36.000). In that year, the Vaal River rose to flood the town and at its height the river was level with the railway bridge. Flood waters gushed into the steelworks and caused considerable damage - a minor calamity when compared with the tragic events of the following year.