In the meantime, on 10 March 1988, when the defence of Cuito Cuanavale after three failed SADF-attacks was secure, Cuban, FAPLA and SWAPO units advanced from Lubango to the southwest. The first South African resistance was encountered near Calueque on 15 March followed by three months of bloody clashes as the Cubans progressed towards the Namibian border. By the end of May Cuba had two divisions in southwestern Angola. By June they constructed two forward airbases atCahama and Xangongo with which Cuban air power could be projected into Namibia. All of southern Angola was covered by a radar network and SA-8 air defence ending South African air superiority.
On 26 May 1988, the chief of the SADF announced, "heavily armed Cuban and SWAPO forces, integrated for the first time, have moved south within 60km of the Namibian border". The remaining SADF forces at Cuito Cuanavale were now in danger of being closed in. On 8 June 1988 the SADF called up 140,000 men of the reserves (Citizen Force), giving an indication of how serious the situation had become. The South African administrator general in Namibia acknowledged on 26 June that Cuban MIG-23s were flying over Namibia, a dramatic reversal from earlier times when the skies had belonged to the SAAF. He added, "the presence of the Cubans had caused a flutter of anxiety" in South Africa.
In June 1988 the Cubans prepared to advance on Calueque starting from Xangongo and Tchipa. In case of serious South African counterattacks, Castro gave orders to be ready to destroy the Ruacana reservoirs and transformers and attack South African bases in Namibia. The offensive started from Xangongo on June 24 immediately clashing with the SADF en route to Cuamato. Although the SADF was driven off the FAPLA-Cubans retreated to their base. On 26 July 1989 the SADF shelled Tchipa (Techipa) with long-range artillery and Castro gave orders for the immediate advance on Calueque and an air strike against the SADF camps and military installations around Calueque. After a clash with a FAPLA-Cuban advance group on 27 June the SADF retreated towards Calueque under bombardment from Cuban planes and crossed the border into Namibia that same afternoon. By then, Cuban MiG-23s had carried out the attacks on the SADF positions around the Calueque dam, 11 km north of the Namibian border, also damaging the bridge and hydroelectric installations. The major force of the Cubans, still on the way, never saw action and returned to Tchipa and with the retreat of the SADF into Namibia an 27 June the hostilities ceased.
The CIA reported that "Cuba's successful use of air power and the apparent weakness of Pretoria's air defences" highlighted the fact that Havana had achieved air superiority in southern Angola and northern Namibia. Only a few hours after the Cuban's air strike, the SADF destroyed the nearby bridge over the Cunene River. They did so, the CIA surmised, "to deny Cuban and Angolan ground forces easy passage to the Namibia border and to reduce the number of positions they must defend." The South Africans, impressed by the suddenness and scale of the Cuban advance and believing that a major battle "involved serious risks" withdrew. Five days later Pretoria ordered a combat group still operational in southeastern Angola to scale back to avoid any more casualties, effectively withdrawing from all fighting, and a SADF division was deployed in defence of Namibia's northern border.