Queen Elizabeth supported Antonio’s claim to the throne as a means of preserving the alliance with Portugal and preventing England’s enemy, Phillip II of Spain, from controlling the Portuguese empire. The English Armada was tasked with seizing Lisbon, which was hoped would encourage nobles loyal to Antonio to rise up in revolt.
The final objective was to seize the Azores, where Antonio, the English friendly claimant to the throne was currently running his government in exile. Furthermore it was hoped that the Azores could serve as an English naval base to attack Spanish treasure fleets returning from the Americas. The combined English and Dutch fleet that set sail in 1589 was 126 ships strong, including 6 royal galleons. In addition to the sailors manning the ships there were over 18,000 soldiers to execute the sieges of Corunna and Lisbon.
Right from the beginning the Armada suffered setbacks. They decided not to attack Santander, choosing instead Corunna where there was only one Spanish galleon under repair. Corunna itself was fortified with 13th century walls and housed 1,500 veteran Spanish troops. After 14 days the English had only managed to seize part of Corunna, and fled when the wind changed direction and news of an incoming Spanish relief force arrived. The Armada lost 3 large ships and 1,500 men in the fighting, with a further 3,000 soldiers and 24 boats leaving the Armada.
The situation degraded even further when the Armada reached Lisbon. The Portuguese refused to revolt in favour of Antonio, and Lisbon was defended by 7,000 Spanish and Portuguese troops. With no siege artillery there was no hope for the city to be seized. One of the English commanders, the Earl Of Essex, still attempted a siege. As supplies dwindled, soldiers succumbed to disease and ships were picked off by Spanish galleys, the Armada fled back to England. Over the course of the Armada 40 English ships had been destroyed or captured, and around 13,000 English soldiers had died. None of the objectives were achieved and Spanish naval supremacy resumed the following year.