The Four Days Battle was a naval battle of the Second Anglo-Dutch War. Fought from June 11 to June 14, 1666 off the Flemish and English coast, it remains one of the longest naval engagements in history.

On learning that the French fleet intended to join the Dutch at Dunkirk, the English decided to prevent this by splitting their fleet. Their main force would try to destroy the Dutch fleet first, while the White Squadron under Rupert was sent to block the Strait of Dover against the French - who didn't show up.

The English fleet of 56 ships commanded by George Monck, 1st Duke of Albemarle, was outnumbered by the Dutch fleet of 85 commanded by Admiral Michiel de Ruyter. The battle ended only after both fleets had expended most of their ammunition.

The Dutch inflicted significant damage on the English fleet. The English had gambled that the crews of the many new Dutch ships of the line would not have been fully trained yet but were deceived in their hopes: they lost seventeen ships, thousands of men and two admirals, Sir Christopher Minns and Sir William Berkeley. HMS Sovereign of the Seas was knocked out of the battle after she lost so many sailors that she could no longer move or fire her cannon.

On the third day the English retreated to the west. The grounded Prince Royal surrendered with admiral George Ayscue and was burned. In the evening Rupert, having already on the first day been ordered to join Monck, at last appeared with twenty ships.

Thus enforced Monck again attacked in line on the fourth day. But the Dutch had the weather gauge: the English attack faltered, their line was broken, the Dutch started to surround them. While the English regrouped to break free to the west, De Ruyter decided to break off the fight. His own fleet was heavily damaged too and he feared to run out of gunpowder while Rupert's squadron still had a sufficient supply.

It was the biggest sea battle of the Second Anglo-Dutch War. However, the outcome proved inconclusive, with both sides claiming victory. Though the Dutch fleet was eventually forced to retreat because of lack of gunpowder, they had managed to cripple the English fleet. The contemporaneous Dutch view on this matter is expressed in a famous epigram by the poet Constantijn Huygens:

Two fight - and for their lives.

The one that caused the row

is beaten - but survives.

And boasts: "I've won it now!"

Two months later the recuperated English fleet challenged the Dutch fleet again, now much more successfully at North Foreland in the St. James's Day Battle. Though this proved to be a victory, the Dutch fleet again wasn't destroyed and the enormous costs of repair after the previous battle had depleted the British treasury, so the Four Days Battle is usually seen as a decisive strategic victory for the Dutch.

de:Seeschlacht der vier Tage nl:Vierdaagse Zeeslag