On the death without a male heir of his half-brother, King Ferdinand I, in October 1383, strenuous efforts were made to secure the succession for Beatrice, Ferdinand's only daughter. As heir presumptive, Beatrice had married king John I of Castile, but popular sentiment was against an arrangement in which Portugal would have been virtually annexed by Castile. The 1383–1385 Portuguese interregnum followed, a period of political anarchy, when no monarch ruled the country.