 This collection was then the base of an exposition inaugurated on August 24, 1920, by President António José de Almeida, marking the centenary of the Liberal Revolution of 1820.The exposition resulted in an interest by the City Council in creating a permanent military museum in the city.By 1957 the commandant-in-chief of the Military Region of Northern Portugal, based in Porto city, conducted a study in order to adapt the Castle of São João da Foz, at Foz do Douro parish, for a museum.