By the early 1970s, FRELIMO's 7,000-strong guerrilla force had wrested control of some countryside areas of the central and northern parts of Mozambique from the Portuguese authorities. The independentist guerrilla was engaging a Portuguese force of approximately 60,000 military, which was almost all concentrated in the area of Cahora Bassa where the Portuguese administration was finalising the construction of a major hydroelectric dam, one of many facilities and improvements that the Portuguese provincial administration's development commission was rapidly developing since the 1960s. The 1974 overthrow of the Portuguese ruling regime after a leftist military coup in Lisbon, brought a dramatic change of direction in Portugal's policy regarding its overseas provinces, and on 25 June 1975, Portugal handed over power to FRELIMO and Mozambique became an independent nation.