The South African government formed the South African Overseas Expeditionary Force in July 1915, as its contribution to the British war effort against the Central Powers. As South African legislation restricted the Union Defence Forces to operating in southern Africa, an entirely new force, made up of volunteers, had to be raised for service in other theatres of war. As they were not officially a South African force, the SAOEF was placed under British operational command for operations on the Western Front. Many volunteers came from UDF units, but they enrolled as individuals, not as contingents, and there was no formal link between SAOEF and UDF units as such. The SAOEF consisted of several arms of service:
1st South African Infantry Brigade. The brigade was commanded by Brigadier General H.T. Lukin and consisted of four regiments recruited from existing military units as well as amongst civilians. Regiments were raised in the four provinces of South Africa:
* The 4th SA Infantry Infantry Regiment was led by Lt Col F.A. Jones, DSO and became known as the "South African Scottish." Lt Col Jones was killed in fighting in Benfray Wood on 11 July 1916 and was replaced at the Battle of Delville Wood by Major D.M. MacLeod. The regiment was raised from the Cape Town Highlanders Regiment and the area of Cape Town while members of 1st Bn Transvaal Scottish Regiment made up most of B Company. C Company came from 2nd Bn Transvaal Scottish Regiment and recruits encouraged by the Caledonian Societies of Natal and Orange Free State made up D Company.
SAOEF units and formations did not serve as distinct South African forces, but were integrated into the British imperial armies and divisions in the field.
During the East African Campaign, there was strong South African participation and leadership. SA Field Artillery, the 1st and 2nd SA Mounted Brigades, the 2nd and 3rd SA Infantry Brigades, and the Cape Corps fought in British operations against German forces in German East Africa from January 1916 until the war in Africa ended on 25 November 1918. Two South African generals, Lt. Gen. Jan Smuts and Lt. Gen. Sir Jacob van Deventer, commanded the operations. Their major battles were: Salaita Hill, Kilimanjaro, and Kondoa-Irangi in 1916; and Behobeho, Narungombe, and Nyangao in 1917. Captain William Anderson Bloomfield won the Victoria Cross for gallantry.
The 1st SA Infantry Brigade was deployed in British operations against the Sanusi in Egypt from January to March 1916. It fought in the Action of Halazin and the Action of Agagiya.
The SA Heavy Artillery and the 1st SA Infantry Brigade fought in the trenches of the Western Front against German forces in France and Belgium, from May 1916 until the war in Europe ended on 11 November 1918. They fought in the battles of the Somme in 1916; Arras, Ypres, and Menin in 1917; and Passchendaele, Messines, Mont Kemmel, and Cambrai in 1918. The two events of the campaign that are still commemorated are the Battle of Delville Wood, and the sinking of the troopship SS Mendi, with the loss of more than 600 African members of the South African Native Labour Corps. Two SAOEF members, Pte William Frederick Faulds and L Cpl William Henry Hewitt, won the Victoria Cross for gallantry.
The SAOEF units and formations were disbanded in 1919. As there were no formal links between SAOEF units and the Union Defence Forces units which had provided their initial manpower, the SAOEF's war record, including its many honours, was not perpetuated by the UDF.
