Aubin Heyndrickx, a Belgian criminal toxicologist, professor and senior UN consultant on chemical weapons, stated that "'there is no doubt anymore that the Cubans were using nerve gases against the troops of Mr. Jonas Savimbi'" (Evans and Novak Jan. 1988). Poison gas residue of Soviet origin was found, for example, on Cuban prisoners of war who had lost a battle at Cuito Cuanavale (ibid.). The UN Security Council recognized that the Cuban Air Force had used chemical weapons, such as gases VX and sarin, in 1988 during the war in Angola after Belgian toxicologists found evidence to that effect (Diario Las Américas 13 July 1999).

In testimony provided to the South African Truth and Reconciliation Commission in 1998, Wouter Basson, former director of South Africa's chemical weapons programme in the 1980s, stated that his country "was forced to develop chemical weapons after Cuban forces used chemical agents against SA troops fighting in Angola" (Business Day 28 July 1998; The Washington Times 19 May 2002)

More proof here from Jane's Defense Weekly.

Conversation above: "Assad YOU CHUMP!!! Take my advice, amigo! Get some "Syria Experts" on your payroll..but hire GOOD ONES. Make sure they're tight with the media and can read from your propaganda releases with conviction and maybe with a smile. Then watch this bad press dissipate...I mean, ever heard anyone denounce ME for using Sarin Gas? Shit man, the very UN that reported my use of Sarin Gas later appointed Cuba to its Human Rights commission! My "Experts" don't come cheap. But they sure earn their pay!"