Operation Thunderbolt (9 March – late April 1997) was the codename for a military offensive by the South Sudanese SPLA rebel group and its allies during the Second Sudanese Civil War. The operation aimed at conquering several towns in Western and Central Equatoria, most importantly Yei, which served as strongholds for the Sudanese Armed Forces (SAF) and helped the Sudanese government to supply its allies, the Ugandan insurgents of the WNBF and UNRF (II) based in Zaire. These pro-Sudanese forces were defeated and driven from Zaire by the SPLA and its allies, namely Uganda and the AFDL, in the course of the First Congo War, thus allowing the SPLA to launch Operation Thunderbolt from the Zairian side of the border. Covertly supported by expeditionary forces from Uganda, Ethiopia, and Eritrea, the SPLA's offensive was a major success, with several SAF garrison towns falling to the South Sudanese rebels in a matter of days. Yei was encircled and put under siege on 11 March 1997. At the same time, a large group of WNBF fighters as well as SAF, FAZ, and ex-Rwandan Armed Forces soldiers was trying to escape from Zaire to Yei. The column was ambushed and destroyed by the SPLA, allowing it to capture Yei shortly afterward. Following this victory, the South Sudanese rebels continued their offensive until late April, capturing several other towns in Equatoria and preparing further anti-government campaigns.
