To South African Minister of Defence P.W. Botha it was evident that the MPLA had gained the upper hand; in a memo dated late June 1975 he observed that the MPLA could "for all intents and purposes be considered the presumptive ultimate rulers of Angola...only drastic and unforeseeable developments could alter such an income." Skirmishes at the Calueque hydroelectric dam, which supplied electricity to South West Africa, gave Botha the opportunity to escalate the SADF's involvement in Angola. On 9 August, a thousand South African troops crossed into Angola and occupied Calueque. While their public objective was to protect the hydroelectric installation and the lives of the civilian engineers employed there, the SADF was also intent on searching out PLAN cadres and weakening FAPLA.