England and Spain had actually been allies for much of the 16th century. But that had changed by the 1580s and relations had become outwardly hostile.
Neither monarch particularly trusted the other. Philip II of Spain was unpopular in England as the former husband of Mary I, a champion of Catholicism and head of the most powerful country in Europe. Elizabeth was considered untrustworthy and a heretic by Philip. However, they tolerated each other provided neither posed too much threat to the other's interests.
In 1568, the Spanish invaded the Netherlands. This became a great problem for the English because Elizabeth, as a Protestant monarch felt bound to help the Dutch. It was also politically expedient to stop the Spanish army from taking over the Netherlands because from here, it would be easy for them to invade England.
By 1584, the Spanish, under the excellent military leadership of the Duke of Parma, seemed to be winning complete control. In 1585, the situation was so grave that Elizabeth felt compelled to send English troops and a large amount of money to support the Dutch rebels. She also sent an expedition of 25 ships with Sir Francis Drake to attack Spanish ports in the Caribbean.
The two countries were now drifting towards war.
The Building of the Great Armada
By late 1585, Philip II decided on his invasion plans. His project was called 'the Enterprise of England'. The Spanish army and its commander, the Duke of Parma were in the Netherlands. Philip planned to send a huge fleet to the Netherlands, meet up with Parma and ferry the army to England.
The Armada was a hugely ambitious project. At 130 ships it was the largest fleet ever known. It cost two-thirds of the entire revenue from the Spanish Empire to build. Contributions - both in money and men- came from all over the empire.
But its mission was plagued by huge practical problems. How could the fleet meet and load up with Parma's army, when there was no suitable deep water port in Spanish control? How could they avoid attacks from the Dutch rebels? How could they sail the channel avoiding English attack? Many of Philip's advisers including the Duke of Parma opposed the expedition, but the king, who felt he had a just cause, was determined.
The Armada was delayed in 1587 by an English raid on the Spanish port of Cadiz which succeeded in destroying or capturing 35 ships in the harbour. But it set sail in summer of 1588 under the command of the hardworking but inexperienced Duke of Medina Sidonia.
The Armada in Action
In July 1588, the Armada sailed up the English Channel in a defensive crescent formation. They were spotted and followed by the English fleet which had set off from Plymouth. The English hoped to block the Spanish attempts to meet up with Parma or at least destroy as much of the Armada as possible.
There were a number of skirmishes between the two fleets off Portland and the Isle of Wright, which caused little damage to the Armada. The Armada continued up the Channel until Medina Sidonia received word that Parma's army was not yet ready. On 7th August, he decided to anchor the fleet at Calais and wait.
This left the Armada dangerously exposed. The English sent fire ships into the Spanish fleet, which caused chaos, with many ships having to cut anchor and abandon their crescent formation. The next day on 8th August, seeing their chance, the English attacked and the final battle was fought off Gravelines. The English fleet, under experienced commanders such as Sir Francis Drake, John Hawkins, and John Frobisher, had smaller, faster vessels and were able to out manoeuvre and probably out fire the Spanish ships.
The remnants of the Armada regrouped. Cut off from their route back to Spain by the English fleet, they were forced to make the treacherous journey north around Scotland and Ireland. They lost more ships and men, before arriving back to Spain.