Dunkirk (Dutch for 'Church in the dunes') was a strategic port on the southern coast of the English Channel in the Spanish Netherlands that had often been a point of contention previously and had changed hands a number of times.

The siege would last a month and featured numerous sorties by the garrison and a determined relief attempt by the Spanish army under the command of Don Juan of Austria and allied English Royalists led by Duke of York and rebels of the French Fronde under the Great Condé that resulted in the battle of the Dunes.

The French, in 1657, completed an alliance with the Lord Protector, Oliver Cromwell, in which the English Commonwealth would join in the war against Spain and supply troops and ships for a campaign in the Spanish Netherlands.

The treaty was renewed in 1658 and encouraged by the promised additions the French were early into the field capturing a contingent of Spanish troops in Cassel, marching by way of Bergues on Dunkirk.

[3] Though often marching and wading through deep water holding their arms over their heads, French morale remained high and roads were made for their baggage and artillery.

Young King Louis XIV and Cardinal Mazarin were personally involved nearby arranging for supplies and ammunition, first at Mardyke and then, at Turenne's urging, Calais.

Trenches were opened on the Downs side of Dunkirk on the night of 4/5 June and finished with the arrival of more troops from France and the 6,000 man English contingent.

The garrison sallied out under cover of the sand and filled in the point of the trench killing or wounding about 100 soldiers of the regiments of Picardy and Plessis.

On the Dunes, one English Royalist regiment continued to stand its ground and fight until a couple of French officers under a truce pointed out that the rest of their army had retreated.

With the loss of its stubborn and active governor, no hope of relief, and the French now lodged at the foot of the last work,[1] Dunkirk surrendered on 25 June after a siege of 22 days from the opening of the trenches.

By this treaty France gained Roussillon and Perpignan, Montmédy and other parts of Luxembourg, Artois and other towns in Flanders, including Arras, Béthune, Gravelines and Thionville, and a new border with Spain was fixed at the Pyrenees.

Cardinal Mazarin honoured the terms of the treaty with Oliver Cromwell and handed the port over to the Commonwealth in exchange for Mardyck captured earlier by the French in 1658 and held by the English.

While the French received all of Artois, England had eliminated the greatest Spanish privateering base[15] and the number of captured English merchant ships carried into Flemish ports was halved in 1657–58.