its sailing ships by steam or mixed propulsion ships, its principal warships becoming the mixed-propulsion corvettes for the high seas operations and the gunships mainly for coastal and colonial patrols. In 1880, the Portuguese fleet included an armored corvette, six corvettes, 13 gunships, three training ships and four support ships. At the end of the 19th century and, specially, following the Berlin Conference called for by Portugal, the navy participated in the Portuguese exploration and mapping of the interior of Africa. From the Portuguese explorers of the African hinterland, stood out the naval officers Hermenegildo Capelo, Brito Capelo and Roberto Ivens that made several expeditions since the late 1870s. Hermenegildo Capelo and Roberto Ivens made the first land connection between Angola and Mozambique, crossing the interior of Africa by unexplored territory, leaving the west coast in January 1884 and arriving at the east coast in September 1885. In this period, the Navy also focused on the mission of the naval defense of Lisbon, complementing its ground defense. This was part of the national strategy which considered that the defense of Portugal would be assured by the defense of its capital and most important city. As part of this mission, in 1876, the Portuguese Navy acquired the ironclad Vasco da Gama, its first armored vessel, intended to operate as a floating coastal defense battery. The plans for the naval defense of Lisbon would also include the use of torpedo boats and submarines, that are later also acquired. In 1882, the Portuguese Navy receives its first torpedo boat and, in 1884, it receives the corvette Afonso de Albuquerque, its first unprotected cruiser. In 1889, Naval Lieutenant João Augusto Fontes Pereira de Melo presented the project of a "submarine station". A model of the so-called submarine Fontes was tested in the Naval Arsenal of Lisbon. At the end of the 19th century, the Portuguese Navy had the conscience that it did not have a capable force to defend the Portuguese European waters and ports against a possible enemy aggression. The Portuguese naval theorists started to defend the use of the submarine as the only weapon capable to face a more powerful enemy navy. In 1896, an emergency naval program proposed by the Navy Minister Jacinto Cândido da Silva was approved. This included the construction of four protected cruisers, which replace the mixed propulsion corvettes as the primary ships of the fleet. A fifth