Armed Forces Day took place on 21 February in Port Elizabeth. The date isn't just one chosen out the air but rather was selected to commemorate the sinking of the SS Mendi.
SS Mendi was a British 4,222 GRT passenger steamship that was built in 1905 . In 1916 during the First World War the UK Admiralty chartered her as a troopship. On 21 February 1917, a large cargo steamship, Darro, collided with her in the English Channel south of the Isle of Wight. Mendi sank killing 646 people, most of whom were black South African troops. The sinking was a major loss of life for the South African military, and was one of the 20th century's worst maritime disasters in UK waters.
The Mendi had sailed from Cape Town carrying 823 men of the 5th Battalion the South African Native Labour Corps to serve in France. She called at Lagos in Nigeria, where a naval gun was mounted on her stern. She next called at Plymouth and then headed up the English Channel toward Le Havre in northern France, escorted by the Acorn-class destroyer HMS Brisk.
Mendi's complement was a mixture characteristic of many UK merchant ships at the time. Officers, stewards, cooks, signallers and gunners were British; firemen and other crew were West Africans, most of them from Sierra Leone.
The South African Native Labour Corps men aboard her came from a range of social backgrounds, and from a number of different peoples spread over the South African provinces and neighbouring territories. 287 were from Transvaal, 139 from the Eastern Cape, 87 from Natal, 27 from Northern Cape, 26 from the Orange Free State, 26 from Basutoland, eight from Bechuanaland (Botswana), five from Western Cape, one from Rhodesia and one from South West Africa. Most had never seen the sea before this voyage, and very few could swim. The officers and NCOs were white South Africans.
At 5 am on 21 February 1917, in thick fog about 10 nautical miles (19 km) south of St. Catherine's Point on the Isle of Wight, the Royal Mail Steam Packet Company cargo ship Darro accidentally rammed Mendi's starboard quarter, breaching her forward hold. Darro was an 11,484 GRT ship, much larger than Mendi, sailing in ballast to Argentina to load meat. Darro survived the collision but Mendi sank, killing 616 South Africans (607 of them black troops) and 30 crew. Some men were killed outright in the collision while others were trapped below decks. Many others gathered on Mendi's deck as she listed and sank. Oral history records that the men met their fate with great dignity. An interpreter, Isaac Williams Wauchope, who had previously served as a Minister in the Congregational Native Church of Fort Beaufort and Blinkwater, is reported to have calmed the panicked men by raising his arms aloft and crying out in a loud voice.
"Be quiet and calm, my countrymen. What is happening now is what you came to do...you are going to die, but that is what you came to do. Brothers, we are drilling the death drill. I, a Xhosa, say you are my brothers...Swazis, Pondos, Basotho...so let us die like brothers. We are the sons of Africa. Raise your war-cries, brothers, for though they made us leave our assegais in the kraal, our voices are left with our bodies."
The damaged Darro did not stay to assist. But Brisk lowered her boats, whose crews then rescued survivors.
Info from Wikipedia