Spain's 'Invincible' Armada included 130 ships, 8,000 seamen and 18,000 soldiers manning thousands of guns. The fleet was headed for Flanders, where it would meet the Duke of Parma and ferry 30,000 troops across the Channel onto England's shores.
It was impossible to keep preparations for such a huge enterprise secret and spies brought news of the plan to England's queen, Elizabeth I.
She agreed to a pre-emptive strike by Francis Drake, who raced to Spain with a small fleet and sunk dozens of the armada ships as they waited in port at Cadiz, an action that the English celebrated as the “singeing of the king of Spain’s beard.”
This delayed the Spanish attack by months, giving England time to strengthen its defences, digging trenches across beaches, securing a giant chain across the Thames and placing alert beacons along the coast.
England's navy was smaller than the Armada, with Drake and Lord Charles Howard leading around 100 ships. But they armed their boats with long-range guns, in contrast to the Spanish fleet that was geared to fighting at close quarters.
The two forces first faced each other in July. The English flotilla attacked from distance but was unable to break the Spanish ships' defensive half-moon pattern.
As the Armada raced towards the Channel, the English continued to harass and harry their attackers, without a decisive impact.
The Spanish dropped anchor off the coast of France, where they hopped to meet up with the Duke of Parma.
Desperate to prevent the two forces combining, the English waited until nightfall and set light to eight empty ships, letting the wind and tide take them towards the Spanish.
In panic at the sight of the firefleet, the Armada fled to the open sea. Seeing the Spanish were out of formation, the Royal Navy attacked at close quarters with repeated cannon fire.
The engagement continued through the day, with the Spanish losing four ships and several more damaged. The attack stopped when the English range out of shots and supplies.
On the coast, English troops were preparing for an invasion. Queen Elizabeth, dressed in armour and a white velvet gown, gave her famous Tilbury speech to inspire her men:
"I know I have the body of a weak and feeble woman; but I have the heart and stomach of a king, and of a king of England too... I myself will take up arms, I myself will be your general, judge and rewarder of every one of your virtues in the field."
Back at sea, weather was on the side of the English. A storm carried the battered Spanish ships into the North Sea, ending their plan to link up with the Duke of Parma.
Supplies and morale was low, and disease was ravaging the men. The Spanish decided to abandon their invasion and escape by sailing around Scotland and Ireland.
But the British weather struck again and the fleet was ravaged by storms. Ships sunk, ran aground and were broken apart.
The Spanish had lost 2,000 men fighting the Royal Navy, but they were to lose 13,000 more on the tortuous journey home.
When it arrived in Spain, the 'Invincible' Armada had lost more than half its ships, with just 60 limping home.
Defeat of the mighty Spanish fleet led to celebrations across England, and the island nation was recognised as one of Europe's sea powers, a badge that would drive its plans for centuries to come.
Do you share our passion for Britain's maritime past?
Join our four-day Hearts of Oak small-group history holiday to take an illuminating look at the birth of Britain's naval age.
You'll be led by Andrew Lambert, one of our country's foremost authorities on Britain's maritime history, to visit the shipyards where the British navy was built and the setting where our seafaring plans were sunk for a generation.
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HEARTS OF OAK
HEARTS OF OAK
Photo credit: English fireships cause the Spanish Armada to flee, Philip James de Loutherbourg, Public domain, via Wikimedia Commons