4 May 1978
On 4 May 1978, the South African air force flew over Cassinga, allegedly a Namibian refugee camp in Southern Angola. It was the South African Defence Force’s (SADF) largest airborne operations when close to 400 paratroopers were dropped near the town of Cassinga. The airborne troops bombed the South West Africa People’s Organisation (SWAPO) refugee camp and People’s Liberation Army of Namibia’s (PLAN) military base, SWAPO’s armed wing. The bombing was followed by ground forces to complete the massacre. More than 600 Namibians, mostly women and children were massacred by the SADF airborne troops, and hundreds more were injured. A United Nations (UN) delegation that visited Cassinga a few days after the tragic event reported that what the South Africans did was criminal in legal terms and savage in moral terms.  The brutal attack was called the Battle of Cassinga, Cassinga Raid or Kassinga Massacre.  It was the South African Army’s first major air assault on a SWAPO refugee camp and military base. It was code named Operation Reindeer. A few weeks after the massacre, six hundred Namibian children, most of whom were survivors of Cassinga, arrived in Cuba to study. Cuba opened its doors widely and generously to the Namibian refugees. The South Africans government claimed that it was just a retaliatory raid against the SWAPO forces who had invaded Namibia with small strikes, and they (South Africans) had claimed to have withdrawn and had not left any South African forces in Angola. However, there has been continuous debates around the Battle of Cassinga as to whether Cassinga was a refugee camp or a military camp or both, and therefore if the raid was a massacre of civilians or a highly successful military operation. The 4 May is now called Cassinga Day and is a national public holiday in Namibia remembering the Battle of Cassinga. 
References

Gleijeses, P. (nd). The Massacre of Cassinga. Available on:https://amadlandawonye.wikispaces.com/The+Massacre+of+Cassinga,+Piero+Gleijeses [accessed on 4 May 2015]|Mike, M (2011).  Battle for Cassinga: South Africa’s Controversial Cross-Border Raid, Angola 1978. African @ war series: Helion and Company publisher. |Mvula, S. (2010). Remembering the Cassinga massacre. Available at: https://www.nshr.org.na/index.php?module=News&func=display&sid=1335 [4 May 2015]|Shipanga, S. (2014). The Cassinga massacre. Available at: https://www.namibian.com.na/indexx.php?archive_id=122802&page_type=archive_story_detail&page=1 [accessed on 4 May 2015]