The Third Anglo-Dutch War or Third Dutch War (Dutch: Derde Engelse Oorlog or Derde Engelse Zeeoorlog) was a military conflict between England and the Republic of the Seven United Netherlands lasting from 1672 to 1674. It was part of the larger Franco-Dutch War. The Royal Navy joined France in its attack on the Republic, but was frustrated in its attempts to blockade the Dutch coast by four strategic victories by Lieutenant-Admiral Michiel de Ruyter. An attempt to make the province of Holland an English protectorate rump state likewise failed. Parliament, fearful that the alliance with France was part of a plot to make England Roman Catholic, forced the king to abandon the costly and fruitless war.

As agreed in the Treaty of Dover, England joined France, having declared war on 6 April 1672 (New Style), by declaring war on 7 April. Many sources incorrectly state the English were the first to declare war on 27 March, a mistake caused by the fact the British were still using the Julian calendar, then ten days behind the Gregorian calendar in use at the Continent. A French army of 130,000, exceptionally accompanied by Louis himself, in two months marched through Liège, bypassed the strong Dutch fortress of Maastricht, advanced along the Rhine, took the Rhine fortresses of Cleves and then on 12 June crossed the Lower Rhine into the Betuwe, thus invading the Republic itself and outflanking the IJssel Line. As a result the province of Overijssel withdrew its troops from the already small Dutch field army to protect its own cities; soon after it capitulated to Bernhard von Galen, the bishop of Münster, who then marched north to occupy Drenthe and lay siege to Groningen. William was forced to fall back on Utrecht, but the burghers refused to let him in. Instead they opened their gates to the French army, to avoid a siege. William withdrew behind the Dutch Water Line, a deliberate flooding to protect the core province of Holland, but the inundations were not ready yet, only having been ordered by the States of Holland on 8 June and hampered by villages unwilling to let the water damage their property.

Meanwhile the first sea battle had taken place. After the English declaration of war, the States-General had increased the naval budget with 2.2 million guilders. De Witt, seeking a decisive naval victory, had decided on an aggressive strategy and sent out De Ruyter with the mission to destroy the Allied fleet. On 7 June he surprised it when re-supplying on the English coast, it was only saved from a severe defeat in the Battle of Sole bay by a sudden turning of the wind, causing De Ruyter to lose the weather gage. Nevertheless the damage incurred was so extensive that the Allies would be prevented from executing major naval actions for the rest of the season. A blockade of the Dutch coast failed. Johan de Witt's brother Cornelius de Witt had accompanied the fleet to make the States regime share in the glory, but the events on land nullified this.

The sudden appearance of a hostile army in the heart of the Republic caused a general panic. The States of Holland on 14 June decided to ask peace conditions from France and England. This convinced Louis that the war was already won and on the advice of de Louvers he began negotiations to reach a treaty as favorable as possible for France. The city populations rioted, blaming the States regime for the disaster and calling for the Prince of Orange to take over government. Most city councils turned Orangist or were even replaced by threat of force with Orangist partisans. Charles had always supported the Orangist faction; now they repaid him with accusing the States faction of wanting to betray the land to the French and depicting Charles as the only man able and willing to save the Dutch from French subjugation. In Dutch history, the year 1672, the national annus horribilis, subsequently became known as the "Year of Disaster" (Rampjaar). A Dutch saying was coined to describe the situation of the state: Redeloos, radeloos, reddeloos, meaning: "reasonless" (the people), "clueless" (the authorities), "rescue less" (the country).

In fact the situation wasn't as immediately desperate as the population believed. De Witt had assumed the conflicting interests of England and France would prevent their successful cooperation. The two kings, motivated by a shared lust for revenge, had managed to put their differences aside as long as their immediate common goal of humiliating the Republic had not been reached yet. Now that it was, each began to worry the other would benefit too much from the war; neither would allow a complete domination of the Republic, and its huge mercantile assets, by his formal ally. When a Dutch mission arrived suing for peace, Louis only demanded Delfzijl, by far the least important port Charles considered, for the English. Yet, when he was offered the southern fortresses of the Republic — the French possession of which would make the Spanish Netherlands indefensible — and ten million guilders, he refused. Knowing that the mission was not allowed to make any concessions on the point of religion and the territorial integrity of the provinces themselves (the southern fortress cities of Breda, 's-Hertogenbosch and Maastricht were in the Generality Lands) Louis demanded — besides twenty million guilders and an annual embassy from the States-General to Louis asking pardon for their putridity — either religious freedom for the Catholics or lordship over Utrecht and Guilders, merely to humiliate the Dutch a bit further. Still he didn't continue his advance fearing to drive the Dutch into the hands of Charles. He waited while the mission returned to ask for new instructions, which would take some time given the decentralized nature of the Dutch administration; all the city councils would have to be consulted on the issue. Meanwhile the water gradually filled the polders of the defense line. On 7 July the inundations were fully set and the province of Holland was safe from a further French advance. Louis wasn't overly worried by this; he was very much focused on Amsterdam and, an early attempt to take the city by a sudden cavalry assault having failed, had decided in any case to avoid an expensive and inevitably very muddy siege by waiting till winter when he expected — reasonably so in the Little Ice Age — to be able to advance over the ice.  

Johan de Witt Death

After the arrival of Johan de Witt the city guard was sent away to stop plundering farmers, the farmers were not found. Without any protection against the assembled mob the brothers were doomed. They were taken out of the prison and killed on their way to the scaffold. Immediately after their death the bodies were mutilated and fingers toes and other parts were cut off. The heart of Cornelis de Witt was exhibited for many years next to his brother's by one of the ringleaders, the silversmith Hendrik Verhoeff. Nowadays most historians assume that his adversary and successor as leader of the government stadtholder William III of Orange was involved. At the very least he protected and rewarded the killers.

On 4 January 1674 the States-General drafted a final peace proposal. On 7 January a Dutch trumpeter arrived in Harwich, carrying with him two letters for the Spanish consul. Though the herald was promptly arrested by the town mayor, the letters were sent to Lord Arlington, who hurriedly brought them in person to del Fresno; Arlington was in turn on 15 January impeached by Sir Gilbert Gerard for high treason as by this very act he had shown to have secret dealings with the enemy. On 24 January the consul handed the letters, containing the peace proposal, to Charles, who pretended to be greatly surprised by this, although he had especially recalled Parliament, prorogued by him in November, for this occasion that very same day. While addressing both Houses the King first emphatically denied the existence of the Treaty of Dover and then produced the peace proposal to the great satisfaction of the members — who in turn had to pretend surprise although Parliament had been informed beforehand by the Dutch of the full content. After some days of debate the treaty was approved by Parliament. This news was met with open joy by the populace. Charles now sent his own trumpeter who was received by the States-General on 1 February. His message was that Charles could announce the absolute agreement of himself and Parliament on this matter, to which institution he gladly deferred. On 5 February a Dutch trumpeter arrived in London, carrying the response of the States-General. That very day Parliament advised the King to conclude a "speedy peace". A Royal Commission was appointed to make a final draft; the Treaty of Westminster was signed by the King on 9 February Old Style, 19 February New Style, 1674. It was ratified by the Lord Keeper on 10 February by placement of the Great Seal; on 17 February it was publicly proclaimed. It was approved by the States of Holland and West Frisia on 4 March (New Style) and ratified by the States-General on 5 March. Due to the different calendars in use in the two countries and the complex procedure, when a single date is given the literature is not in agreement.