In 1421, when the Portuguese began the southwards exploration of the West African coast under Prince Henry the Navigator, their primary aim (there were several) was to find the source of wealthy goods being brought to the city of Ceuta.
There came a time when an additional aim developed, which was to find a direct sea route to India. When was this decision taken? Was it taken when the Portuguese obtained a copy of the Fra Mauro map in 1459 showing the Atlantic and Indian Oceans meet at the southern point of Africa, i.e., indicating a route to India was possible?
The Fra Mauro map carries the comment,
Many have thought, and many have written, that the sea does not encompass our habitable and temperate zone on the south but there is much evidence to support a contrary opinion, and particularly that of the Portuguese, whom the king of Portugal has sent on board his caravels to verify the fact by ocular inspection.
This implies the Portuguese were seeking to round Africa before they received a copy of this map — a map that was first created about 1450.