<P> In 1297 , with the Portuguese part of the reconquista completed , King Dinis of Portugal took personal interest in exports and in 1317 he made an agreement with Genoese merchant sailor Manuel Pessanha ( Pesagno ) , appointing him first admiral of the Portuguese navy , with the goal of defending the country against Muslim pirate raids . Outbreaks of bubonic plague led to severe depopulation in the second half of the 14th century : only the sea offered alternatives , with most population settling in fishing and trading coastal areas . Between 1325 and 1357 Afonso IV of Portugal encouraged maritime commerce and ordered the first explorations . The Canary Islands , already known to the Genoese , were claimed as officially discovered under patronage of the Portuguese but in 1344 Castile disputed them , expanding their rivalry into the sea . </P>
who began the age of exploration in portugal
Afonso IV of Portugal