The Spanish Armada was a Spanish naval fleet (army of ships) that was most famous for being used by King Philip II of Spain against England in 1588. The ships were on their way to Flanders, across the English Channel, to fetch an army to invade England. However, the Royal Navy of England during Queen Elizabeth I of England’s reign caught up with the ships on the way. The English defeated the Armada by using the wind, twhich blew the ships, to light them on fire into the anchored fleet. This started on 12 July 1588 and ended during August 1588.

The second-in-command of the Royal Navy was Sir Francis Drake. A story is that he was playing a game of bowling with his friends when he heard of the attack, but he boldly insisted that he had time to finish the game and then to defeat the Spanish Armada. The story was first written 100 years after the events, however, and so it may have never happened.

The Spanish Armada was led by Spanish Duke of Medina Sidonia. He had no naval experience but replaced the original commander, who had died in February.

Reasons
The Anglo-Spanish War of 1585 to 1604 had several causes:
 Religion: Years of religious differences led up to the conflict between Catholic Spain and Protestant England. Philip II particularly feared the spread of Protestantism in England. He wanted to conquer England to bring it back to Catholicism and so also had the support of the Pope.
 Trade: The Spanish saw England as a competitor in trade and in expansion to the ‘New World’ (America).  This led to many skirmishes (irregular fights) between the English pirates and privateers and the Spanish vessels.  English sailors targeted Spanish shipping around Europe and the Atlantic. 
 Politics: The turning point came following the execution of Mary, Queen of Scots, Spain’s Catholic ally.  The killing of Mary was ordered by Elizabeth and was the final straw for Philip II, Mary’s husband, after tensions between England and Spain.
 Spanish Netherlands: England, as a Protestant nation, continued to interfere in the Netherlands in support of Protestantism there and undermined Spanish influence.
In April 1587, while the Armada was being prepared, Sir Francis Drake’s burned over 20 Spanish ships in the Spanish port of Cadiz .

Defeat 
The Spanish defeat of the Armada is often attributed to a severe storm that scattered the Spanish vessels before they met the British fleet. The Spanish could not use the many more ships they had to their advantage as planned. The English had only 55 ships. They were not bigger but carried more guns.  The Spanish had only short-range cannons, but the English had long-range cannons. Part of the English strategy was to sink or damage the enemy ships before they got close enough to fire back at them.

The English ships were also more manoeuvrable. The Spanish galleons could have their oars broken off completely by a heavy vessel sailing past nearby. The morale and dedication of the British sailors was high and ewas improved by the famous speech by Queen Elizabeth and loyalty to England. They also were led by experienced captains, who had years of naval battles behind them. 

The defeated Spanish fled north through the North Sea with the English chasing them. Many more ships were lost, and thousands of men died during the retreat. 

Even though the English sailors had done so well, they failed to get paid and were made to stay on their ships and 'Guard' in case there was another Spanish attack. Lord Howard of Effingham was shocked,when he found out that his soldiers were not getting paid. He said. "I would rather have never a penny in the world, than they (his sailors) should lack...." (I would rather die poor than see my men go unpaid).

A year later, Queen Elizabeth of England sent a similar English Armada of more than 100 ships and 19,000 troops to complete her victory. It was to seize a fleet of Spanish treasure ships and to impose a new king on Portugal. However, that expedition also failed.  

A second Spanish Armada in 1596 and a third in 1597 also failed.

Reasons for failure

Unrealistic expectations
King Philip II of Spain had a poor understanding of his plan of action. He believed that God was on his side, which was a faulty understanding of reality.

Francis Drake’s raid on Cadiz
As the Armada was being prepared, English Admiral Sir Francis Drake launched a daring raid on the Spanish port of Cadiz, which disrupted the Spanish preparations and forced the invasion to be postponed until 1588.

Duke of Medina-Sidonia
The Duke of Medina-Sidonia had been selected for not his skills as an admiral but his noble birth. He was not very confident to lead such a huge armada against the English naval ships.

Lack of experienced gunners
The Spanish lacked experienced gunners on their ships. On the other hand, the English fleet roughly had one man in ten as a gunnery specialist. That meant that that every gun crew was supervised by someone with the relevant skills and experience. As a result, when the battle came, the English fired two or three times faster.

Poorer ammunition
The Spanish carried more ammunition for their cannons than the English, but it was not as good. Iron ore in Spain was inferior in that found in England. The situation was made worse by the rush to produce ammunition for the expedition. To speed production, cannon balls had been cooled in water, which weakened their structure.

The Weather
Even before they reached their destination, the Spanish ships had been scattered by storms twice. Some were damaged, others were lost, and there were long delays while they regrouped. That was an omen of what was to come, with storms smashing the fleet as it fled the English. It then limped home around the British Isles.

Fire ships
The English used fire ships against the Spanish fleet but did not sink any enemy ship. However, they forced the Spanish to scatter, and ships were damaged as they collided with each other. That gave the English an advantage in the days that followed.

Other websites 
 Spanish Armada Citizendium
 

History of Spain
History of the British Isles
Royal Navy
Crusades