The South Africans began Operation Moduler on 13 August with Sierra Battery unleashing 120 mm mortar fire on the 47 and 59 Brigades halting their advance at Catato Woods. On 16 August the South African forces were given permission to release their
G5 battery and a
Ratel-90 anti-tank squadron for operations on the Lomba River. On the early morning of 20 August, South African Valkiri MRLs opened fire on FAPLA forces at Catato Woods alerting the Angolans for the first time that the South African were assisting
UNITA. This rocket firing would continue for the next five days on the FAPLA brigades. During this period the Ratel-90 anti-tank squadron was advancing north to
Mavinga while between 26 and 28 August,
SAAF C-130s flew in the eight G5 battery and their support equipment for deployment to the
Lomba River region. Between 24 and 28 August, a special forces team from
4 Reconnaissance Regiment were sent on a mission called
Operation Coolidge. With the South African force now called 20 Brigade, Colonel
Deon Ferreira took command on 5 September with the force divided into Battle Groups Alpha, Bravo and Charlie with units from 20 Artillery Regiment divided between them as necessary. By 7 September, 61 Mechanised Battalion had now reached an area 25 km south-west of Mavinga. UNITA scouts reported that FAPLA's 21 Brigade was attempting a crossing of the Lomba/Gomba River 12 km east of Cunzumbia on 9 September. Combat Group Bravo sent its Ratel 90 anti-tank squadron forward with a company from 101 Battalion and they encountered a fording BTR-60 that they destroyed but FAPLA artillery counter-attack and it forced the South African units to withdraw 6 km away. The detached unit of Combat Group Bravo returned on 10 September to the fording site on the Lomba River and again attacked elements of 21 Brigade, but the Angolans' counter-attacked sending in three tanks. The Ratel-90s failed to stop the tanks' advance, so the new Ratel ZT3s were brought into the battle, firing seven missiles with four successful strikes on the tanks. MiG aircraft then arrived over the battle site and forced the South African units to withdraw but they had stopped 21 Brigade's advance. 47 Brigade, based at the source of the Lomba River, moved two battalions with three tanks eastwards to try to make contact with 59 Brigade. On 13 September, the SADF countered this advance by sending two companies from 101 Battalion, eight Ratel-90s and four Ratel ZT3s westwards to meet the FAPLA battalions. Artillery attacked the FAPLA positions first before the small SADF unit attacked and stopped the advance with FAPLA battalions losing 200 dead or wounded but the Angolan tanks led a counter-attack on the Ratels, killing seven SADF soldiers before losing five of their own tanks. The small SADF unit called in their reserve, Combat Group Charlie, and heavy fighting continued for several more hours before a withdrawal was called when further FAPLA tanks were summoned and
101 Battalion company's cohesion broke down and some fled the battle. 47 members of the unit would later be discharged from the army after that event because they were concerned about their deployment against tanks and use as UNITA's "mercenaries". The same SADF unit would again encounter the FAPLA tanks around midnight and destroyed two tanks before withdrawing again. On 16 September, Combat Group Alpha (61 Mech) began its attack in the early morning but its movement was slowed by dense bush and only encountered elements of 47 Brigade who by this time knew the South Africans were coming so by later afternoon Alpha withdrew with no success losing one killed and three wounded. The SAAF kept up the pressure on 47 Brigade with three attacks on 21 September by four
Buccaneers around 08h50, four
Mirages around 13h00 and four Buccaneers around 17h50. The SAAF conducted a strike against 21 Brigade on 25 September but they missed the target by 200 m but SADF artillery continued their bombardment and the FAPLA brigade took heavy losses. The SAAF sent six Mirage F1CZs to attempt to intercept Angolan MiG-23s on 27 September with one Mirage suffering tail damage from an Angolan
air-to-air missile. It returned to SWA-Namibia but crash-landed at the airfield. 47 Brigade received orders on 28 September to cross the Lomba River and meet up with 59 Brigade and then move eastwards crossing the Cunzumbia River and link up with 21 Brigade but the orders were changed later and 21 Brigade was ordered to withdraw north-eastwards. Later that night, President
PW Botha, Defence Minister
Magnus Malan and the generals flew into Mavinga and met Deon Ferreira and his officers the following day for a briefing. President Botha decided on a more offensive operation and the release of any SADF forces required to destroy the remaining FAPLA brigades east of Cuito Cuanavale. On 30 September, 47 Brigade attempted to link up with 59 Brigade but their advance was forced back by a SADF artillery bombardment. Plans had been made to attack 47 Brigade on 5 October but radio intercepts reported that FAPLA was about to move from their position, so on 3 October, Combat Group Charlie was ordered to attack with air and artillery support, four UNITA battalions and a 32 Battalion company in reserve. Around 10h17, the Ratel-90s caught the Angolan soldiers crossing the river while the South Africans were attacked by tanks and ZU-23 anti-aircraft guns and the Angolan MiGs flying in support of the ground troops but failed in destroying any SADF vehicles. The South Africans withdrew to resupply around 12h00 and resumed their attack from 14h00 with the Angolans now attempting to retreat across the river taking even more casualties but the battle was over by 17h00. SAAF aircraft attacked 59 Brigade during the day preventing the brigade from coming to the aid of 47 Brigade. The FAPLA casualties were around 600 killed, the loss of a dozen tanks and vehicles and 47 Brigade no longer a cohesive unit while the SADF lost one soldier killed and a Ratel destroyed and captured a highly sophisticated
SA-8 anti-aircraft missile system – the first time the weapon had fallen into western hands. The same day saw plans formulated for 32 Battalion to send units to attack and disrupt the FAPLA supply lines between Menongue and Cuito Cuanavale. ==FAPLA retreats from the Lomba River region==