Mail service between the Republics and the two British colonies governed by conventions between them and by their membership of the Universal Postal Union almost ceased from mid October 1899. Internal post within the South African Republic and with the Orange Free State continued.
Ways of avoiding the embargo on mail to Europe via the colonies were replaced by routing it via neutral Portuguese territory, to be carried on German and other shipping lines. As Boer units invaded parts of Natal and Cape Colony some mail passed usually to destinations in the Transvaal.
With the reversal of fortune when British-led Army retook captured land and then invaded Republican territory crossing the Vaal river in March 1900, local postal services closed. The British Army Post Office organised for official use and used by soldiers were supplied with stationery and stamps currently available in the UK. Distinctive post marks from army units as the second British Occupation of Transvaal progressed along the railways which supplied rations and munitions.
Postal services were reopened from June 1900 using overprinted stocks of stamps and stationery, with V.R.I. or E.R.I. to validate their use. Mail between Transvaal and prison camps from as far as Bermuda, St Helena and Ceylon (now Sri Lanka) as well as Cape Town are evidence of the ways in which the Boer prisoners kept in touch with those who remained in Transvaal.
New stamps and postal stationery bearing the profile of King Edward VII were commissioned for the new Colony before the Peace Treaty was signed at Vereeniging at the end of May 1902.