In order to control spice trade, the Portuguese established small forts to resupply ships and conquered cities in east Africa.
Spice trade was the trade between ancient civilizations in Asia, Northeast Africa and Europe.
The Portuguese and Spanish established themselves by building forts and trading out of them.
Portugal established a pepper monopoly by 1504, and the importance of spice relied on the fact that spices were useful to mask the flavor of rancid or spoiled meat. For instance, meat was preserved by salting it.