became well known throughout the country for their ruthlessness in hunting down insurgents. The Portuguese Army steadily pushed the UPA back across the border into Congo-Kinshasa in a brutal counteroffensive that also displaced some 150,000 Bakongo refugees, taking control of Pedra Verde, the UPA's last base in northern Angola, on 20 September 1961. Within the next few weeks Portuguese military forces pushed the MPLA out of Luanda northeast into the Dembos region, where the MPLA established the "1st Military Region". For the moment, the Angolan insurgency had been defeated, but new guerrilla attacks later broke out in other regions of Angola such as Cabinda province, the central plateaus, and eastern and southeastern Angola. By most accounts, Portugal's counterinsurgency campaign in Angola was the most successful of all its campaigns in the Colonial War. Angola is a large territory, and the long distances from safe havens in neighboring countries supporting the rebel forces made it difficult for the latter to escape detection. The distance from the major Angolan urban centers to the neighboring Democratic Republic of the Congo and Zambia were so large that the eastern part of Angola's territory was known by the Portuguese as Terras do Fim do Mundo (the lands of the far side of the world). Another factor was internecine struggles between three competing revolutionary movements – FNLA, MPLA, and UNITA – and their guerrilla armies. For most of the conflict, the three rebel groups spent as much time fighting each other as they did fighting the Portuguese. For example, during the 1961 Ferreira Incident, a UPA patrol captured 21 MPLA insurgents as prisoners, then summarily executed them on 9 October, sparking open confrontation between the two insurgent groups. Strategy also played a role, as a successful hearts and minds campaign led by General Francisco da Costa Gomes helped blunt the influence of the various revolutionary movements. Finally, as in Mozambique, Portuguese Angola was able to receive support of South Africa. South African military operations proved to be of significant assistance to Portuguese military forces in Angola, who sometimes referred to their South African counterparts as primos (cousins). Several unique counter-insurgency forces were developed and deployed in the campaign in Angola: Batalhões de Caçadores Pára-quedistas (Paratrooper Hunter Battalions): employed throughout the conflicts in Africa, were the first forces to arrive in Angola when the war began. Comandos (Commandos): born out of the war in Angola, they were