The Battle of Lens, fought on 20 August 1648 in the County of Hainaut between the Spanish Army of Flanders and the French Army of Picardy. A clear Spanish tactical defeat but the French could not press on, mainly due to the political instability in Paris and lack of men.
In the Low Countries, the Spanish governor had instructions to take the offensive to distract the French from Catalonia. At the beginning of February, Archduke Leopold sent the Spanish army in a surprise attack against Courtrai but due to the awareness and strength of the French garrison the attack failed (Montglat, volume 2, 1826). The campaign started really in May when the Prince of Conde moved to besiege the city of Ypres. On 12 May he had surrounded the city and on the 19th the line of circumvallation was finished. On the other side, the Spanish commander decided to abandon Ypres and rapidly moved to again attack Courtrai. This time the French garrison (2,000 men) was totally surprised and after few days they had to surrender on 23 May. Coming back to Ypres, the Archduke tried to save the city but on 28 May the Spanish garrison capitulated. In June, the Spanish conducted some operations in Artois and even in France. On 16 June, Field Marshal Rantzau tried to raid the city of Ostend with a fleet of 50 ships and 3,000 men but the Marquis of Sfondrati was waiting for him and managed to annihilate the French force and to capture Rantzau. On 9 August the Archduke captured the city of Furnes after a siege of 10 days. On 18 August, the Spanish had retaken Lens, but two days later the army of Flanders was defeated by the Prince of Conde, losing 8,000-9,000 men.
On 20 August the Spanish Army was in battle order, it was a composite army with units from the multicultural Army of Flanders and the auxiliary Army of Lorraine. The total force is given as 18,000 men with 38 artillery guns. The Spanish were deployed with a right wing of cavalry commanded by the Count of Bucquoy and the Prince de Ligne. In the centre or bataille, in the first line, was a mixture of 10 infantry squadrons and seven cavalry squadrons. Still in the centre, the second line had only six infantry battalions with two cavalry squadrons (guards of the Archduke and guards of Fuensaldana) between the lines. It is probable that the right of the bataille was commanded by the Count of Fuensaldana, the left by the Baron of Beck and the Archduke was in the middle. The left wing was under the command of the Prince de Salms and the Count of Ligneville and was made of a first line of 12 cavalry squadrons and a second line of nine squadrons. Finally we have up to 38 artillery guns located on the hill near Lens, defended by a reserve of four to seven cavalry squadrons as well as light cavalry squadrons of Croats and free companies of dragoons.
Seeing a well-ordinanced force on a hill, the Prince of Conde decided to avoid a futile blind attack and fall back to find supplies in La Bassee. The French began to move in six columns. On the other side the French movement was seen with surprise and the Archduke sent the cavalry of the Count of Ligneville supported by mangas of musketeers or dragoons to harass the French rearguard. The French rearguard was badly defeated and Conde tried to answer with his heavy cavalry but he was also bitten and was obliged to run away behind the French infantry. This first success was encouraging for some Spanish officers, and the Archduke was quickly convinced to move all the army to the previous French position. On the other side, the Prince of Conde understood that a retreat in such conditions could lead to a disaster and decided to stop and face the incoming Spanish. Thus, the Count of Ligneville halted his attacks and as quickly as possible the French commander reorganised his army'” with 17 cavalry squadrons45 on the right under his command, the infantry in the centre commanded by the Gaspard of Coligny on the left, 16 squadrons47 of cavalry under the command of Field Marshal Gramont and a reserve of five squadrons commanded by Colonel Erlach.
With such arrangements, the French moved forward to retake their previous positions. Following Canovas del Castillo (Volume 2, 1888), when the first fighting started on the Spanish left the Spanish army had not finished its deployment, the cavalry was in place but some of the infantry was just arriving on the battlefield and the reserve squadrons were still on the hill in their original position.
On the French right, Conde was able to disperse the Spanish cavalry of the first line with ease, but he was successfully counter-attacked by the cavalry of Lorraine of the second line. During sometime the French and Lorraine cavalry fought bravely but like at Rocroi, the cavalry of the French reserve managed to outflank their opponents. Attacked on the flank by Erlach and from the front by Conde the cavalry of Ligneville started to give ground step by step and in the end they ran away from the battlefield. On the other cavalry wing, the men commanded by the Count of Bucquoy clashed with their enemies, holding their position while exchanging pistol fire and sword thrusts with the French cavalry of Gramont. Finally, the superior organisation of the French cavalry took the upper hand and the Spanish cavalry started to step back and to abandon the battlefield. Meantime in the centre the French infantry led by the battalions of the Gardes Franfaises and Gardes Suisse launched a massive assault on the Spanish infantry (Bonifaz and Mouroy/Beck). Successful at first, they were soon isolated from their comrades suffering terrible losses after a counterattack by the Spanish tercios (Toledo and Vargas) and the cavalry of the centre. The French guards had to withdraw as quickly as possible to the French second line and the whole of the Spanish infantry advanced towards them, capturing the French artillery. The Spanish were halted by the strong resistance of French infantry of Picardy, Persan and Gardes Ecossaises, the attack of the squadrons of gendarmes and by the support of the French second line. Rapidly, soldiers of the Spanish infantry discovered that their flanks were open and that the Spanish cavalry had abandoned them. Panic started to spread in the Spanish centre and some of the infantry withdrew with the last cavalry squadrons present on the battlefield. On the other side, the two French wings managed to trap a good proportion of Spanish infantry and to overcome the last resistance of the reserve cavalry. In the following hours the French captured hundreds of Spanish including a wounded Baron of Beck. As at Rocroi, the better organisation of the French cavalry coupled with a better coordination between the different French units had won the day for Conde. As usual Spanish losses are difficult to establish, but following Spanish sources, losses could be estimated at 3,500 men (infantry only), while French accounts elevated the number to 8,800 men or 10,000 men. To our knowledge, the estimate of Galeazo Gualdo (1651), should be close to the truth and if we take into accounts some deserters Spanish losses could be estimated at up to 6,000 men, most of them infantry, 38 guns and the majority of the baggage. On the other side, French losses were estimated at 600 men excluding officers (Galeazo Gualdo, 1651).
On 27 August, the victorious French army was again besieging Furnes and on 10 September with no hope to be succoured, the garrison capitulated. The news from Paris was not good at all for the monarchy and the Prince of Conde was recalled to re-establish civil order. The situation in the French kingdom was not as good as it seemed. The total war imposed by Richelieu and by Mazarin had increased strongly the taxes to maintain the army. By spring 1648, a general discontent was spreading in all classes of the population. In Paris the events started on 15 January when the parliament of Paris refused to sign seven tax edicts to finance the war. During spring and most of summer and despite the effort of Mazarin, the judicial officers of the parliament not only continue to refuse to pay but also condemned all the financial schemes of the monarchy. With the victory of the Prince of Conde in hand, Mazarin decided to arrest the leaders of the parliament, but the feeling of the common people of Paris was against him and on 27 August, during “la journee des barricades” the people of Paris erupted in open rebellion. The rebellion of the parliament of Paris called la fronde parlementaire (1648- 1649) was followed by the rebellion of the nobility (1650- 1653). The Fronde was the last rebellion of the French nobility against the monarchy but at the end it facilitated the emergence of absolutism. For the Spanish the Fronde was an opportunity to retake the control of what had been lost and to bring the war to France.