Air Force, as the semi-autonomous Naval Air Forces. The Naval Air Forces would be fully integrated in the Air Force in 1958, definitely ceasing to exist as a separate branch, with many of the naval aviators and other personnel opting to return to the Portuguese Navy. In the early 1960s, the Portuguese fleet includes 16 ocean escorts (including destroyers, frigates and avisos), three submarines, 23 patrol vessels, 19 mine warfare vessels (including ocean mine-sweepers, coastal mine-sweepers and mine-hunters), four survey vessels, one tanker, one buoy tender and one training ship. From the late 1950s, the Portuguese Government and Military begin to concern about the increasing external and internal threats against the overseas territories of Portugal and the consequent need to defend them, including with adequate naval forces. Besides, the "European" navy equipped mainly with anti-submarine frigates, submarines and mine warfare vessels to operate in the North Atlantic in the scope of NATO, a new "Overseas" navy starts to be planned. Initially, the planned Overseas navy is conceived as mobile intervention force, centered in light aircraft carriers carrying Marine assault forces. However, this concept is not considered the most adequate and soon evolves to a concept of force centered in frigates and corvettes capable of carrying and supporting small landing forces, as well as in patrol ships. The beginning of the separatist guerrillas in the early 1960s and the consequent need of operating in the rivers and lakes of the Portuguese Africa would force the evolution of the Overseas navy concept, with the creation of brown-water forces, equipped with a high number of small patrol and landing craft. In parallel to developing its fleet, the Portuguese Navy starts to expand its worldwide capacity of command, control and logistics in order to cover all Portuguese Overseas territories and respective waters. From 1957, naval commands are created in Cape Verde, in Angola, in Mozambique and in Goa (Portuguese India), besides those established in the Continent and in the Azores. Each naval command is responsible for an oceanic area of operations, in a way that most of the North Atlantic, the South Atlantic and the Indian Ocean are contiguously covered by Portuguese oceanic areas. Subordinated to the naval commands, a number of local maritime defense commands and naval support facilities are also created. The Portuguese Navy also develops a worldwide communications network, with naval radio stations being established in all Portuguese Overseas territories. This