Siege of Mons ( 1572 ) The Siege of Mons of 1572 took place at Mons , capital of the County of Hainaut , Spanish Netherlands ( present - day Belgium ) , between June 23 and September 19 , 1572 , as part of the Eighty Years ' War , the Anglo - Spanish War ( 1585 – 1604 ) , and the French Wars of Religion . In the spring of 1572 , after the capture of Valenciennes by a Protestant force under Louis of Nassau , the Dutch commander continued with his offensive and took Mons by surprise on 24 May . After three months of siege , and the defeats of the armies of Adrien de Hangest , Seigneur de Genlis , and William the Silent , Prince of Orange " ( Dutch : Willem van Oranje ) " , by the Spanish army led by Don Fernando Álvarez de Toledo , Duke of Alba ( " " The Iron Duke " " ) , Governor - General of the Spanish Netherlands , and his son , Don Fadrique de Toledo , Louis of Nassau ' s forces , isolated and without any hope of help , surrendered Mons to the Duke of Alba on September 19 . < ref name = " Hernán / Maffi p . 24 " > Hernán / Maffi p . 24 < / ref > Background . In early May , 1572 , Louis of Nassau , one of the major commanders of the Dutch rebel forces , encouraged by the victory at Brielle by the Sea Beggars ( 1 April ) , and supported by the Huguenot leader Gaspard de Coligny , invaded the Spanish Netherlands with an army composed by German , English , Scottish and French soldiers , and took Valenciennes on 21 May . On May 23 , Louis of Nassau arrived at Mons with 1 , 000 infantry and 500 cavalry , who encamped in the environs of the city . At the next day , after finding out the schedules of opening of the doors of Mons , Nassau entered the city by surprise with the cavalry , and then , the rest of his forces , defeating the small Spanish garrison . Louis took control of the city , and a few days later , was reinforced by about 4 , 500 infantry and cavalry under the command of the Count of Montgomery . When the news reached the Spanish headquarters , Don Fernando Álvarez de Toledo , Duke of Alba , Governor - General of the Spanish Netherlands , and commander - in - chief of the Spanish forces in the Low Countries , sent his son Don Fadrique with 4 , 000 soldiers ( other 16 , 000 soldiers were coming from the north ) , along with the " Maestre de Campo " Chiappino Vitelli , to defeat Louis of Nassau and retrieve Mons . On June 23 , Fadrique ' s forces arrived at Mons and laid siege to the city . Furthermore , in early June , the Duke of Alba , at the head of the bulk of the Spanish army , recaptured Valenciennes after a feeble defence of the Protestant garrison , depriving the rebels , and their French allies , of one of their main bases . Meanwhile , William of Orange , Prince of Orange , had recruited in Germany an army of 14 , 000 soldiers of infantry and 3 , 000 of cavalry ( 11 , 000 infantry and 6 , 000 cavalry according to other sources ) , and on July 7 , William crossed the Rhine , entering the Netherlands . Siege of Mons . Louis of Nassau , aware of the progress of his brother , sent Adrien de Hangest , Seigneur de Genlis , to France for more reinforcements , and in mid - July , Genlis , with an army of 10 , 000 men , crossed the border again , and marched towards Mons . Louis sent a message to Genlis , urging that he should join to the army of his brother , William of Orange , but Genlis ignored the message , and advanced against the Spaniards . Battle of Saint - Ghislain . On July 19 , Genlis and his forces encamped near Mons , in a circular plane . Don Fadrique , aware his arrival , advanced towards him with 4 , 000 infantry , 1 , 500 cavalry , and 3 , 000 armed villagers for the occasion . Genlis sent a detachment to reconnoitre , but after seeing the advance of the Spanish forces , these troops retreated to the French camp at full speed . " Don Frederic de Toledo is coming upon us " , they cried . The Spanish cavalry of Philip of Noircarmes , without delay , charged against the French army , followed by infantry , while the rear was protected by the cavalry of Don Bernardino de Mendoza . The attack caused panic among the French Huguenots , and then , the Spanish infantry shattered the French army . The Spanish victory was complete , and the army of Genlis was entirely routed . About 2 , 000 French soldiers were killed or wounded , and 700 captured , including 70 nobles and officers ( in the following days , more than 4 , 000 were captured ) . The leader of the French army , Adrien de Hangest , was also captured , and taken prisoner to Antwerp . The Captain Francisco de Bobadilla was honored with carrying the news of the victory to the King Philip II , for the proven value during the battle . Meantime , the Prince of Orange with his new army continued to advance towards Mons . On July 23 , after the capture of Roermond , his troops mutinied . On August 27 , with guarantees of payment of some cities in Holland , crossed the Meuse , advancing over Diest , Termonde , Oudenaarde and Nivelles . St . Bartholomew ' s Day . On August 11 , Gaspard de Coligny , with the approval of the King Charles IX , had written to the Prince , that he expected soon to begin his march towards the Netherlands . However , in France , Charles IX lost his nerve , fearing a Spanish invasion and a Catholic rebellion if he persisted in the planned invasion of the Netherlands to support the Huguenots and the Dutch Protestants . The result was St . Bartholomew ' s Day massacre on August 23 . When the news reached to the Netherlands , affected the morale of the Protestant troops ( especially in the army of Louis of Nassau at Mons , because great part of his troops were Huguenots ) , while in the Spanish camp was celebrated by bonfires and illuminations , even in the St . Michael and St . Gudula Cathedral , the Catholic population sang anthems in honor of " " the most Christian King of France " " . In early September , Don Fernando , Duke of Alba ( who despite being a strong defender of Catholicism , described the massacre as a atrocity ) , arrived at Mons with reinforcements and took command of the operations . The Prince of Orange continued to advance through the Netherlands , and some cities and villages were forced to open the doors to its passage for fear ( Alba was specially angry for this ) , although some , such as Leuven , prevented the Orange ' s troops entered the city , in exchange for supplies . On September 10 , arrived near Mons , and Alba , knowing the Orange ' s arrival , positioned his troops for a possible attack . William of Orange ' s army . At the same day , as expected , the Orange ' s cavalry attacked the flank of the Spanish army , but was repulsed by the Spanish arquebusier s , led in first line by the Duke of Alba , his son Don Fadrique , and the Duke of Medinaceli , causing multiple casualties in the Orange ' s cavalry . After the failed attack , the Prince retreated to the village of Harmignies , about a league of Mons . At the night on September 11 , the Spanish commander , " Maestre de Campo " Julián Romero , entered the camp of William of Orange commanding 600 arquebusiers , remaining as a reserve , in rear , the same number , supported by units of infantry and light cavalry , whose purpose was to protect the withdrawal . In this raid 600 rebels were killed , for only 60 Spaniards . Hundred of horses were captured , and a great part of the tents and the supplies were destroyed and burned . During the action , William of Orange himself was in profound slumber , and was saved by her Spaniel dog ' s barking , who slept beside him . With a heavy heart , William wrote to his brother Louis of his forlorn condition and inability to relieve Mons . The Prince retreated with his army to Nivelles and Mechelen , marching to the Rhine , and finally the bulk of his troops , mutinous for lack of pay , dispersed towards Germany . Thereafter he made his way almost alone to Holland , the only province which still remained true to him . Surrender . After the defeat of the army of French Huguenots under Adrien de Hangest , and the withdrawal of the army of William of Orange , Louis of Nassau found himself isolated in Mons . Even the French Huguenots under his command mutinied as a consequence for the support of the King of France to the massacre of St . Bartholomew . On September 19 , Louis of Nassau surrendered Mons to the Duke of Alba , and were agreed the terms of the capitulation between the Dutch and the Spaniards . Consequences . Louis of Nassau would be received by the Duke of Alba , the Duke of Medinaceli and Don Fadrique . The city would be evacuated on September 21 , and on September 24 , the Duke of Alba entered Mons . Philip of Noircames , by his position as Governor of Hainaut , took command of the city . All towns that had accepted the authority of Prince William of Orange , many for fear of reprisals , returned to the allegiance to the Duke of Alba . However , Alba advanced over Mechelen , one of the cities that lent support to the Orange ' s army , and where the Prince had left a small garrison . In retaliation for the assistance provided by the city to the rebel army of William of Orange , and to satisfy the arrears of pay of the soldiers of the Spanish regiments , the Duke of Alba ordered to the troops under the command of his son Don Fadrique sack the city . After dealing with Orange ' s threat in the south , Alba sent his son Don Fadrique to the two rebellious provinces Gelderland and Holland . Fadrique started his campaign by the capture of the fortress - city of Zutphen in Gelderland . On his way to Amsterdam , Don Fadrique came across Naarden , which surrendered on November 22 , 1572 .