Siege of Luxembourg ( 1684 ) The Siege of Luxembourg , in which Louis XIV of France ( husband of Maria Theresa of Spain ) laid siege to the Spanish - controlled Fortress of Luxembourg from 27 April to 7 June 1684 , was the most significant confrontation between France and Spain of the War of the Reunions . The action caused alarm among France ' s neighbours and resulted in the formation of the League of Augsburg in 1686 . In the ensuing war France was forced to give up the duchy , which was returned to the Habsburgs by the Treaty of Ryswick in 1697 . Background . An important element of Louis XIV ' s policy of reunion was to the gain the strategically important city of Luxembourg , which was under Spanish rule , but belonged " de jure " to the Holy Roman Empire . The city had been besieged in 1681 - 1682 , and the inhabitants endured great hardship . This attempt was broken off , but the country was occupied . Louis started the War of the Reunions especially to conquer Luxembourg in 1683 . In December of that year , Luxembourg was bombarded with mortars . About 6 , 000 bombs and grenades were fired . The Fortress of Luxembourg did not , in those days , have modern fortifications , but was instead protected by its geographic location . Unlike the city , much of which was destroyed by the previous year ' s bombardment , the defensive works were in good condition . Siege . In January 1684 , the French Marshal François de Créquy succeeded in cutting Luxembourg off from the main Spanish army . An army was posted between Brussels and Luxembourg , in order to distract the enemy troops from the actual objective . Sébastien Le Prestre de Vauban was in command of the siege of Luxembourg . The French troops numbered 25 , 000 men , and had more than 70 guns . Their forces included a group of military engineers . The Spanish troops in the city were commanded by the Prince de Chimay and the Comte de Tille . They included about 4 , 090 men and 600 horses . They were complemented by 600 residents , who had volunteered . The city and fortress lacked provisions and ammunition . The siege started when defensive positions were built around the city from 28 April and 8 May , in order to protect the besieging army . About 12 , 000 workers were used , including conscripted farmers . Workers were also brought in from the areas of Metz , Toul and Verdun . The defenders attempted to hinder the work as much as possible . On 1 May there was a major sorty : the workers in the area of the attack were driven off and the defences destroyed , before a counter - attack forced the Spanish to return to the fortress . As the main point of attack , Vauban chose the Front of the plain ( New Gate front ) . Furthermore , an additional point of attack and several feint attacks were planned . From early May , the actual siege trenches were dug . With the help of sap trenches , Vauban approached the fortress in two locations . The closest Front was still half a gunshot away from the covered passages of the city . Both points of attack were linked through a connecting trench . The French set up four batteries for the siege artillery , which were aimed at the main point of attack . Along with normal guns , mortars were used . In the night of 8 May , the cannons started firing on the city . The defenders reacted on 9 May with several sorties and destroyed several offensive buildings , but could not stop the construction work . On 11 May the besiegers were within 30 steps of the closest covered passage of the fortress . Three parallels connected the trenches . Additional gun batteries were brought in . At other locations , the trenches were also nearing the city . From the 14 May , both sides started a mine war , while above ground the attackers were exposed more and more to the fire of the defenders . The latter dug tunnels to undermine the offensive positions and allowed these to collapse . The besiegers especially came under fire from the redoubt s , which therefore became the main target of the guns . On 18 May the French gained entry to one of the partly underground passages of Redoubt Mary , and embittered close combat ensued . The next day , the French expelled the defenders from the redoubt . The Spanish had prepared to blow up the position before leaving , but this failed . After Redoubt Berlaimont came under heave fire for three days , this too was evacuated by the Spanish in the night of 21 May . The attackers now had the entire covered passage under their control , and could now move their guns close to the city . From 24 May , the fortifications in the main area of attack came under massive gun and mortar fire . On 25 May the Spanish were driven out of the interior covered passage after heavy fighting . A mine detonated by them killed many attackers . French sappers started to undermine the walls and to damage them through underground explosions . Thus , on 27 May the Counter - Guard Barlaimont was damaged and then stormed by French troops . They were repulsed later , but managed to blow up the position . On 29 and 30 May the Spanish withdrew from further posts which had become indefensible . Meanwhile , the French miners continued working . On 31 May the defending troops were withdrawn to the main wall . Bastion Barlaimont was also in danger of being taken by an attack after the work by French miners . The governor of the fortress convened a council of war . As there was no hope of a relief army and he feared pillages and massacres in the city after a takeover , he started to negotiate a surrender . These negotiations did not bring results , and the gun fire from both sides became heavier than ever . In the smaller sites of the siege , especially in the area of the castle , the attackers were making breaches . In the end it was clear to the defenders that they could not hold out . On 3 June they raised a white flag and asked for negotiations . Both sides ceased fire , and soon negotiated an honourable surrender . Four days later , the garrison was allowed to leave the city with 1 , 300 to 2 , 000 surviving soldiers ( according to different sources ) with their horses and weaponry . Consequences . During the siege , the French artillery fired bombarded the city day and night with more than 55 , 000 shots . The garrison suffered more than 2 , 700 casualties ( dead , wounded and sick ) . Out of the city volunteers , 80 died . The French suffered losses of 8 , 000 men . The siege not only took many casualties , but was also expensive , costing 373 , 000 Livres . After the city was captured , the French marched to Trier , where they took the city and destroyed the fortifications . After this they marched into the Electorate of Cologne , with the approval of its ruler . After taking Luxembourg , Louis XIV had attained his war aim , and now sought peace , successfully . Vauban rebuilt and enlarged the fortifications of the Fortress of Luxembourg . See also . city