Answer:
The Portuguese became the first global sea power in the 1400s/1500s by developing cutting edge navigation technology and by preventing its trading competitors from early access to navigation records (maps), therefore establishing virtually exclusive trade routes.
As a small nation, Portugal may have appeared to be an unlikely leader in exploration and navigational science. Its geographical position, however, helped to shape its course. Surrounded to the east and north by Spain and having no outlets on the Mediterranean, Portugal was compelled to regard the Atlantic Ocean as its main medium of travel.
There are more lyrical motivations, spanning from religious and political expansion desires by the monarchy, but the main trigger was the poor state of the nation: the country was short on money and fundamental resources (such as grain) at the time, and that worked as a strong catalyst for what would become the beginning of the Age of Discoveries, in a very what do we have to lose kind of way: let’s try to find a new trade route by going where no one else went before.
Step-by-step explanation: