In mediaeval times, treaties, alliances and truces were common but usually they were limited to a specific purpose and a term of years. What makes the Treaty of Windsor of 1386 remarkable is that it was unlimited in time and covered such a wide range of human activity :- military, commercial and social. At the end of the 14th century it is estimated that the populations of Portugal and England were one and two million respectively. Yet these two small seafaring nations were able in forthcoming years to establish world-wide empires and build powerful fleets to enforce their authority.
So it is surprising that, with competition for commercial trading routes and overseas territories so fierce among European nations, reasonably peaceful and co-operative relations between Portugal and England were maintained for almost two centuries. But after 1559 both the French and English governments permitted their privateers to raid shipping and ports in the main Portuguese theatre of the Atlantic Islands and west African coast. Sir John Hawkins formed a squadron specifically to capture the trade of slaves to Spanish America while George Fenner attempted to seize Santiago and the Cape Verde islands. Portugal responded by threatening to declare war on England and for two years all trade was suspended with Portuguese merchant shipping sailing in convoys protected by warships. However, the diplomacy of the legitimate English factors resident in Portugal enabled a Treaty to be concluded in 1576 whereby England had trading rights in Madeira and Azores but was excluded from the west African coast.
The tribulations of Portugal were soon to be exacerbated by the ill-advised decision of the young king Sebastian to extend the construction of Portuguese fortresses along the coast of Morrocco and to attempt the conquest of the Maghrib . His expeditionary force was overwhelmed in August 1578 at the disastrous battle at Alcácer-Quivir where he and most of his noble army were killed. His successor, Henry the Cardinal-King, tried for two years to restore stability but the Spanish monarch Phillip II moved swiftly to seize Portugal by force and to take possession of the nation and its rich assets for sixty years (1580-1640) during which the provisions of the Anglo-Portuguese Treaties of 1386 and 1576 were extinguished.
Portuguese loyalty to its Spanish masters was soon to be tested by the inclusion of a squadron of ten galleons and two zabras (totalling 4,600 seamen and soldiers) in the “Invincible Spanish Arnada” which sailed from Lisbon in July 1588. By coincidence, they were stationed opposite Calais in the same waters where six galleons had been sent in 1386 by king João I to protect the English Channel ports but, before they could take on board the army of the Duke of Parma, fireships caused damage and gales then drove the armada northwards to encounters storms which were so severe that there was no choice other than to sail around Scotland and then southwards through the Irish sea. The galleons São Mateus and São Filipe ran aground and were lost off the coast of Flanders while the São Marcos was wrecked on the coast of County Clare, Ireland ; most of those aboard were drowned . Four galleons managed to return to Santander and two to Corunna where the São João was destroyed by fire in 1589 by Sir Francis Drake. This venture is the only one recorded of open Anglo-Portuguese hostility until peace with Spain was negotiated by the English in 1605 but trading did not officially resume until January 1642 when king João IV agreed with King Charles I to revive the friendship expressed in the earlier treaties by buying arms and ships and recruiting forces in England, to restore to the London/Lisbon merchants their customs privileges and to respect the protestant religion throughout Portuguese possessions.
For Portugal the first years of restored independence were tumultuous. Spain continued to press its former dominance and was aided by papal influence which left vacant practically all of the Catholic bishoprics in Portugal and its possessions. Holland abandoned its erstwhile alliance and the Dutch West India Company resumed in 1647 its attacks on the Portuguese mercantile fleet causing heavy losses especially in the sugar trade. In 1648 the beheading of king Charles I brought uncertainty to English international relations.
In November 1649 Prince Rupert and a small royalist fleet arrived in the Tagus and was diplomatically received by João IV but when the Commonwealth sent Admiral Blake and a much stronger force the following year , Rupert was forced to leave so that the dispute could be settled at sea. A Portuguese delegation headed by the count Penaguião was sent to London and eventually the Commonwealth Treaty of 1654 was signed with trading terms very much in favour of England. Customs duty was limited to a maximum of 23% with the right of the Lisbon based factors to appoint (and pay!) their own judge , merchant shipping was to have complete access to all Portuguese possessions and English naval ships were to be given a base for provisions and repairs. In return , Portugal was assured of military assistance and this was soon put to the test when Spain attempted a renewed occupation but was defeated by an Anglo-Portuguese force at the battle of Arronches in 1653. The following year the Dutch were routed in Brazil and with overtures of alliance coming from France, things began to look brighter for the Portuguese when Afonso VI acceded to the throne in 1656 with Queen Luisa (of Andalusia) acting as regent for her partly paralysed and dyslexic son.
In Part 4 we will continue with the successive treaties onwards from 1661.