early 1970s, the Navy oriented part of its effort to the Zambezi River. In addition to its commitment in the Mozambican theatre of operations against the independence forces, from 1966, the Portuguese Navy had to maintain an oceanic task force in the Mozambique Channel, composed of frigates on rotation, to deter any possible hostile action from the British naval forces that kept stationed off the port of Beira to try to force the embargo of oil to Rhodesia, following its unilateral declaration of independence. From 1971, the Portuguese naval presence in Mozambique included three frigates or corvettes, one logistical support ship, three patrol boats and one landing craft in the Indian Ocean, five patrol boats and seven landing craft in Lake Nyassa, three Special Marines detachments and three Marine companies. Besides combat operations, the Portuguese Navy continued to provide long-range and coastal logistics to the Portuguese Armed Forces stationed in the several overseas territories of Portugal in the Atlantic (Cape Verde, São Tomé and Príncipe, Portuguese Guinea and Angola), the Indian Ocean (Mozambique) and the Pacific (Portuguese Timor and Macau). The needs to give priority for the acquisition of a large number of small units to operate in the African rivers delayed the plans for the ocean overseas force foresee in the late 1950s. However these plans go forward in the late 1960s, with the building of ships capable of operating both as anti-submarine ocean escorts as to perform overseas patrol and landing operations. These ships are foresee as a modern version of the avisos of the 1930s. For this role, four Comandante João Belo-class frigates are ordered from French yards. In parallel, the Portuguese Navy's engineer Rogério d'Oliveira designs a revolutionary type of ship for the role, that would be the s. These corvettes are the first modular ships of the world, capable of being adapted for several types of missions, including anti-submarine warfare and amphibious operations, at the same time being cheap to operate. Its design would soon be copied, giving origin to a series of frigates and corvettes classes that served several navies. For the operations in Africa, the João Coutinho-class corvettes were designed with small draft to be able to navigate near the coast and in large rivers and had accommodations on board for a force of Marines, being capable of supporting it in landing operations. Six ships of the João Coutinho class are built, these