The United States House of Representatives voted 236 to 185 to repeal the Clark Amendment on 11 July 1985. The MPLA government began attacking UNITA later that month from Luena towards Cazombo along the Benguela Railway in a military operation named Congresso II, taking Cazombo on 18 September. The MPLA government tried unsuccessfully to take UNITA's supply depot in Mavinga from Menongue. While the attack failed, very different interpretations of the attack emerged. UNITA claimed Portuguese-speaking Soviet officers led FAPLA troops while the government said UNITA relied on South African paratroopers to defeat the MPLA attack. The South African government admitted to fighting in the area, but said its troops fought SWAPO militants.
