Portuguese participation in the slave trade 127The royal monopoly did not extend to Brazil, where slaves could enter
freely, in contrast to the Spanish West Indies which were subject to the asiento
system. The original law providing for the collection of export duty on slaves
is not extant : the most plausible document on the subject is one by Abreu de
Brito (1592), in which he gives a figure of 3,000 reis a head when the destina-
tion was Brazil and 6,000 reis for the Spanish West Indies. Joäo Rodrigues
Coutinho seems to have arbitrarily increased the duty by 1,000 reis a head
during the 1600s. The vagueness of the texts and the lack of other sources led
Antonio Carreira to the conclusion that the contractors altered the rate of
duty to suit their own interests and convenience.
Portugal and the slave trade in the seventeenth
and eighteenth centuriesAt the end of the sixteenth century, Portugal underwent a great political change
with the union of the crowns of Spain and Portugal in the person of Philip II
of Spain. The sixty years (1580-1640) of Spanish rule over Portugal were far
more important than this item of domestic politics might at first sight suggest :
indeed, the period marks a turning-point in European colonial history, and
in the development of the American colonies and its corollary, the slave trade.
During the sixteenth century, Portugal's rivals had tried to break her
maritime supremacy in the Atlantic. These attacks were the work of pirates
and traders, and were successfully repulsed. There had been attempts at occupa-
tion and even raids against the coasts of Mina, Guinea, Cape Verde and Brazil ;
and though they were pointers to the envy aroused by the trade in gold, slaves
and sugar, they were no more than sporadic. The French had tried to establish
themselves in Brazil in 1555, and often carried out attacks on shipping. Cape
Verde likewise underwent regular assaults by the French and British: in 1578
Drake even went so far as to try to occupy Mina.
But after the union of the two crowns these activities, which had hitherto
amounted to nothing more than smuggling and piratical forays, became inter-
national conflicts. Attacks directed against the presence of Portugal in Africa
were obviously designed to wrest her trade from her. The wars which Spain
and Portugal faced with the powers of northern Europe had three main objects
as far as Portugal was concerned: to supplant her in her trade with the Orient,
to take over the sugar plantations of Brazil, and (as a sequel) to take over the
sources of African labour.
The union of the two crowns enabled Spain's enemies to turn also against
Portugal; for, though Philip II had decided to leave internal affairs in the hands
of the Portuguese, foreign policy was joint. In this struggle, the most relentless
foes were the United Provinces. Incursions into Africa started in 1598. Then a
twelve-year truce was signed with Holland, in return for the freedom of Portu-