Despite Lord-Protector Cromwell's dream of forging a grand alliance of European Protestant nations, the war against Spain led to closer ties with another Catholic nation: Spain's principal enemy France. It also led to an alliance between Spain and British Royalists exiled in Europe.
The Anglo-French Alliance
In 1654, negotiations between Cromwell and Cardinal Mazarin's ambassador M. de Bordeaux-Neufville resulted in the expulsion from Paris of the exiled Charles II and his entourage; France then agreed to withdraw all support from the Stuarts in a secret clause of a commercial treaty signed in October 1655. With Spain and England openly at war, Charles travelled to the Spanish Netherlands In March 1656 to negotiate with representatives of King Philip of Spain for help in regaining the throne of England. At the Treaty of Brussels, signed on 2 April 1656, the Spanish agreed to provide an army of invasion as soon as the Royalists could secure an English port for their disembarkation. In exchange, Charles agreed that on regaining the throne he would return England's newly-acquired territory in the West Indies to Spain and would also grant concessions to Catholics in his dominions. By a further agreement with Spain, Charles summoned all British subjects fighting in the French army to serve in the Spanish-Royalist force. This raised an additional 2,000 troops by the end of 1656: an English regiment, a Scottish regiment and two Irish regiments with Charles II's brother James, Duke of York, as commander of the British contingent. The two senior regiments of the British army originate in these forces: the Grenadier Guards and the Life Guards.
The projected Spanish invasion depended upon the seizure of an English port and upon the Channel fleet declaring for Charles. The plan came to nothing, however, upon the failure of a Leveller-Royalist conspiracy allegedly involving Vice-Admiral John Lawson.
Meanwhile, Cromwell sent Sir William Lockhart as special ambassador to France with instructions to negotiate a military alliance against Spain. The negotiations were delayed because Louis XIV and Cardinal Mazarin were reluctant to enter an alliance with Protestant England and hoped for peace with Spain instead. But when Spanish demands proved too high, Mazarin turned to the English alliance. The Anglo-French treaty was finally signed in March 1657. It was binding for one year only. England agreed to join with France in her continuing war against Spain in Flanders. France would contribute an army of 20,000 men, England would contribute 6,000 troops and the English fleet in a campaign against the coastal fortresses of Dunkirk, Mardyke and Gravelines. On their capture, it was agreed that Dunkirk and Mardyke would be ceded to England, Gravelines to France. England guaranteed freedom of worship to the Catholic population of Dunkirk. Both nations agreed that they would not negotiate with Spain without the other's consent.
The combined Anglo-French army for the invasion of Flanders was commanded by Marshal Turenne. The English contingent was commanded by Sir John Reynolds. Ranged against them, the Spanish Army of Flanders was commanded by Don Juan-José of Austria and Louis, Prince de Condé.
Early in May 1657, Marshall Turenne mustered 24,000 troops on the borders of Picardy. Rather than march directly against the Flemish ports, which were heavily defended by the Spaniards, Turenne besieged the inland stronghold of Cambrai as a diversionary move. The Prince of Condé relieved the siege of Cambrai in early June and Turenne withdrew to St Quentin where on 11 June, six infantry regiments under the command of Sir John Reynolds joined him. The 6,000 auxiliaries were all English; the Anglo-French treaty had specified that Scots and Irishmen were to be excluded because they could not be trusted to fight against allies of the House of Stuart. Roughly one quarter of the auxiliaries were drafted from the standing army, the rest were volunteers, including many former soldiers who had served in the civil wars. All wore the red coat of the New Model Army.
While squadrons of Cromwell's navy blockaded the Flemish ports, Marshal Turenne spent the summer of 1657 campaigning against the Spanish in Luxemburg and in elaborate manoeuvres for strategic positions inland. The manoeuvres were designed to draw Spanish forces away from the coastal region of Dunkirk and Gravelines, but Cromwell grew increasingly impatient. At the end of August he threatened to withdraw the English regiments unless Turenne marched against the Flemish ports, which were the primary objectives of the campaign. By the time Turenne marched towards Dunkirk in September 1657, sickness and desertion had reduced the English contingent to 4,000 men. Cromwell agreed to send siege artillery, extra supplies and reinforcements. The Channel fleet was mobilised to assist the military operation.
Before moving against Dunkirk, Turenne planned to capture the nearby fort of Mardyke, which commanded one of the best harbours in the region. The Anglo-French army approached Mardyke on 19 September 1657. A line of entrenchments was constructed between Mardyke and Dunkirk to hinder any attempt by the Spaniards to send a relief force, then the allied artillery began bombarding the fort. The outlying defences were overrun on 21 September and the main fort surrendered the following day. As agreed in the treaty, Mardyke was immediately handed over to England.
Cromwell wanted Turenne to march against Dunkirk straight away and offered to send a further 5,000 regular troops as reinforcements for the attack, but Turenne preferred to proceed against Gravelines, which was less strongly garrisoned than Dunkirk. Early in October, however, the attack on Gravelines was abandoned when the defenders broke the dykes to flood the surrounding country. On 22 October, Don Juan-José led a force of 4,000 men from Dunkirk in an attempt to recapture Mardyke before the English could finish repairing and extending the fortifications. Charles II, the Duke of York and the Marquis of Ormond accompanied the Spanish force. The English garrison was assisted by gunfire from ships in the harbour, and the attack was easily repulsed. Sir Edward Hyde later pleaded with Charles II not to risk his life so recklessly in future.
In mid-November 1657, Turenne withdrew the French army into winter quarters. Reynolds was appointed governor of Mardyke and the fort was garrisoned by the English regiments, but troop numbers continued to decline through sickness until fewer than 1,800 men were fit for active service. The garrison lay within five miles of Dunkirk and informal parleys were occasionally held between officers of the two camps. At one such meeting, Reynolds met and conversed with the Duke of York. Although nothing but compliments and civilities were exchanged, the meeting aroused suspicion among some of the officers at Mardyke so that Reynolds felt compelled to return to England to assure the Protector of his loyalty. On 5 December, the ship conveying him home was wrecked on the Goodwin Sands and Reynolds was drowned. He was replaced as governor of Mardyke by Major-General Thomas Morgan.
The Anglo-French alliance of March 1657 was valid for one year only. Cromwell was dissatisfied with the results of the 1657 campaign in Flanders; before renewing the treaty, he insisted upon guarantees from the French that the capture of Dunkirk would be the first military priority of the new campaign. The alliance was duly renewed on 18 March 1658. The English navy resumed its blockade of the Flemish ports and an additional 4,000 infantrymen were sent to reinforce the Anglo-French army. Marshall Turenne mustered his forces at Amiens early in May 1658 and joined forces with Marshal Castelnau and the English contingent before Dunkirk on 15 May.
The allied army besieging Dunkirk was 25,000 strong. Turenne ordered the construction of two lines of entrenchment: an interior line to guard against sorties and attacks from the garrison itself, and an exterior line to hinder any attempt to re-supply or relieve the town. The English fleet blockaded the harbour and kept up a steady bombardment of Dunkirk's seaward defences. The sands and marshes around Dunkirk slowed the progress of the siege works and the garrison, under the command of the Marquis de Lede, made frequent raids on the allied lines. Meanwhile, Don Juan-José of Austria gathered all the men he could muster at Ypres and set out for the relief of Dunkirk. On 3 June 1658, the Spanish army advanced to take up a position in the sandhills to the north-east of Dunkirk. Detailing 6,000 men to guard the siege works, Marshal Turenne ordered the rest of the allied army to be ready to march against the Spaniards at dawn the next day.
The Spanish army occupied a crescent-shaped range of sandhills running down to the sea to the east of Dunkirk. Veterans of the Spanish army of Flanders were deployed on the extreme right, then came the British Royalist contingent led by the Duke of York with one English, one Scottish and three Irish regiments, then a number of German and Walloon regiments. The Prince de Condé's rebel French forces held the left flank. English warships opened fire on the Spanish right flank and prevented the deployment of Don Luis de Caracena's cavalry, which redeployed behind the infantry in the hollows amongst the sand dunes. In total Don Juan-José's army comprised around 7,000 infantry and 8,000 cavalry. The Spanish were not eager to fight because part of their infantry and all their artillery were still moving into position.
Turenne's Anglo-French army halted 500 yards from the Spanish lines on a lower ridge. Supported by Marshal Castelnau's cavalry, seven English regiments under the overall command of Sir William Lockhart and Major-General Morgan held the left of the position facing the Spanish veterans. Turenne's French infantry and two regiments of Swiss Guards occupied the centre, with the Marquis de Créquy's cavalry on the right flank. Turenne commanded a total of 9,000 infantry, 6,000 cavalry and a number of guns.
Without waiting for Turenne's orders, the redcoats advanced to attack the key Spanish position, which was a sandhill 150 feet high held by the regiment of Don Gaspar Boniface. Picked detachments of marksmen fired on the Spaniards while Lockhart's regiment led the assault up the steep slope. Castelnau's cavalry advanced along the beach to support the English advance. On the opposite wing, Créquy's cavalry drove back the first line of Condé's horse. The entire French line surged forward to support Lockhart and Créquy.
Lockhart's regiment was the first to attain the summit of the sandhill, where they fired a volley at the defenders before closing with Boniface's veterans. In a fierce struggle, the Spaniards were driven from the hill. Castelnau's cavalry advanced along the seashore and swept round behind the hill to complete the rout of the Spanish right flank. The redcoats reformed on the hilltop and marched down the far side, where they were immediately charged by the Duke of York's cavalry. York's attack was repulsed with heavy losses but he succeeded in rallying his own troops and the remnants of Boniface's regiment to lead a second attack on the flank of the advancing redcoats. Once again, they resisted stubbornly and, with the arrival of a body of Castelnau's cavalry, the Duke of York retreated.
In the centre, Turenne's French and Swiss infantry quickly overran the Germans and Walloons. The Royalist Irish infantry attempted to make a stand, but they too were overwhelmed. On the Spanish left flank, the Prince de Condé's reserves held firm against Créquy's cavalry and drove them back. Condé regrouped his forces and made several charges against the French and Swiss infantry but with the collapse of the Spanish right flank and centre, Condé's position was hopeless. Around midday, he rallied what forces he could and retreated to Furnes. The Spanish had lost about 1,000 men in the battle, with 4,000 taken prisoner. Turenne's army lost 400, half of whom were from the English regiments.
Following the defeat of the Spanish army, the siege of Dunkirk was resumed. The town held out for a further ten days then surrendered after its governor the Marquis de Lede was killed during a skirmish. As agreed under the terms of the treaty, Dunkirk was ceded to England. On 15 June 1658, King Louis XIV in person handed the keys of the town to Sir William Lockhart, who agreed to honour England's promise to respect the rights of the Catholic population of Dunkirk.
Marshal Turenne continued his campaign against the Spanish in Flanders. After 3,000 English troops had been drawn off to garrison Dunkirk and Mardyke, Major-General Morgan and four English regiments continued to serve with the French army throughout the summer of 1658. Morgan's regiments fought with distinction at the capture of several Flemish fortresses and towns, including Gravelines in August and Ypres in September.
Bernard Capp, Cromwell's Navy: the fleet and the English revolution (Oxford 1989)
C.H. Firth, Cromwell's Army (London 1902)
C.H. Firth, The Last Years of the Protectorate, vols. i and ii (London 1909)
C.H. Firth & G. Davies, The Regimental History of Cromwell's Army, vol. ii (Oxford 1940)
S.R. Gardiner, History of the Commonwealth and Protectorate vols. iii and iv (London 1903)