Between the 15th and 16th centuries, a chain of about 50 Portuguese forts either housed or protected "feitorias" along the coasts of West and East Africa, the Indian Ocean, China, Japan, and South America. The main Portuguese factories were in Goa, Malacca, Ormuz, Ternate, and Macau. They were mainly driven by the trade of gold and slaves on the coast of Guinea, spices in the Indian Ocean, and sugar cane in the New World. They were also used for local triangular trade between several territories, like Goa-Macau-Nagasaki, trading products such as sugar, pepper, coconut, timber, horses, grain, feathers from exotic Indonesian birds, precious stones, silks and porcelain from the East, among many other products. In the Indian Ocean, the trade in Portuguese factories was enforced and increased by a merchant ship licensing system: the cartazes.