Battle of the Dunes

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 towns, including Gravelines on 27 August and Ypres on 26 September.