The siege of Maastricht was a battle of the Eighty Years' War which lasted from March 12 to July 1, 1579. The Spanish were victorious.
The Siege of Maastricht was undertaken in a moment in which the Royal authority had almost collapsed in the Spanish Netherlands. A wave of Protestant, popular violence known as Beeldenstorm had erupted in 1566, leading Philip II to dispatch an army under the Duke of Alba to the region in 1567. Alba prosecuted the Protestants and those whose loyalty to the king was under suspicion, implemented a new episcopal reform and defeated an invasion by William of Orange from Germany. However, his fiscal policies, intended to finance the Spanish Army of Flanders, were highly unpopular and led to a new rebellion in the spring of 1572. This quickly spread across Zeeland, Holland and Gelderland, where the Geuzen and Orange's followers took control of many towns and cities. Alba failed to suppress the revolt and was replaced as governor by Luis de Requesens in 1573. The latter coupled military pressure with political negotiations in order to pacify the Low Countries, yet his efforts failed as a consequence of the Spanish bankruptcy of 1575. His sudden death in March 1576 created a power vacuum. The Council of State, which was to rule the country until Philip II designated a new governor, was divided between opposite factions led by the Spaniard Gerónimo de Roda and the Netherlandish nobleman Philippe III de Croÿ, Duke of Aarschot. Over the summer, the inability of the Spanish military command to pay its soldiers resulted in a series of mutinies which prompted the provinces loyal to Philip II to join forces with those rebellious in the Pacification of Ghent with the common goal of expelling the foreign troops and restore the peace.
The new governor, John of Austria, illegitimate half-brother to Philip, signed the so-called Perpetual Edict on 12 February 1577, ordering the Spanish troops to leave the Netherlands for Italy in exchange for the States General agreeing to recognize him as governor and to maintain the Catholic religion. The Spanish abandoned the country on 20 March 1577, but the reconciliation proved fruitless, as the provinces of Holland and Zeeland were not willing to return to the Royal obedience without the toleration of the Protestant cult. Orange, as stadtholder of the two provinces, refused to accept John as governor and to participate in the States General summoned by the latter. As Orange's influence was growing, John left Brussels for the safer Namur and recalled the Spanish troops. Aarschot, the most influential Southern noblemen, invited Archduke Matthias, future Holy Roman Emperor, to take John's position, which the States declared vacant. When he arrived on 30 October 1577, Orange, thanks to this popularity, had replaced Aarschot as the leading political figure, and Matthias had to content himself to be a figurehead. On 31 January 1578, the Spanish army routed the States General's force at the Battle of Gembloux and took Leuven on 13 February 1578, forcing Orange and Matthias to abandon the now unsecure Brussels for Antwerp. New prospects opened for Philip II, as the largest silver convoy up to the point had reached Seville in August 1577.
While the Spanish Army went on the offensive, growing religious tensions in Flanders and Brabant led to an increasing factionalism. Calvinists took power in Ghent, and the magistrates of Antwerp, Brussels and Mechelen, originating from the lower nobility and the landed aristocracy, were replaced by burghers. The States troops occupied several reluctant towns in the northern provinces, including Amersfoort, and purged its magistracies. In Holland, Calvinists seized power in Amsterdam and Haarlem, and in Zeeland, at Ter Goes. The Catholic majority in the States General blocked an edict of tolerance and, over the summer of 1578, the States of Hainaut, Artois and the Walloon Flanders declared that they would not accept the Protestant cult. In the same way, Holland and Zeeland refused to tolerate the Catholic cult. The Southern Catholic nobility, organized in a faction known as the Malcontents, asked France for help and, on 13 August 1578, the States General procclaimed Francis of Anjou, brother to the King of France, as 'Defender of the liberties of the Low Countries'. In exchange, 12,000 French soldiers would support the States Army against the Spanish. In turn, the Calvinists from Ghent appealed to John Casimir of the Palatinate-Simmern, a Calvinist too, who entered the Netherlands in autumn ahead a German mercenary army. Three factions were now fighting against other.
The Spanish army continued its offensive amidst the Netherlandish inner conflict and made rapid gains. With Leuven secured, John of Austria sent Alexander Farnese, his nephew and close friend, to besiege Zichem. The town was captured, and its garrison executed to discourage further resistance. A quick advance followed: Diest surrendered after a brief negotiation, and Nivelle did the same in early March 1578. Beaumont and Chimay were taken with little or no resistance. On 13 April 1578, the Spanish army was reinforced by the Tercio of the League under Lope de Figueroa, which numbered 2,600 soldiers who had followed the Spanish Road from Milan. Philippeville was then invested and forced to capitulate a few weeks later. Then John went to Namur for a rest and split his army in two different commands. Ottavio Gonzaga, general of the cavalry, was sent to raid the area around Lier and Aarschot, while Farnese, with the bulk of the troops, was tasked with subduing the Duchy of Limburg. On arriving at the capital of the duchy, the town of Limbourg, Farnese ordered an assault over the suburb of Dolhain, which was quickly taken. The artillery was laid shortly thereafter and the States garrison, numbering 1,000 men, surrendered on 14 June 1578. Save for the governor, who was escorted to Aachen, all the States troops joined the Spanish army. Cristóbal de Mondragón, a veteran Spanish colonel of Walloon infantry, was appointed governor of Limburg and ordered to besiege the castle of Dalhem, from where the States troops raided the villages nearby. Despite the strength of the castle, erected over a step rock, it was taken by assault by the Burgundian Regiment of the Baron of Cheveraux, which massacred most of its defenders and residents, to Mondragón's displeasure.
The Spanish army faced an unexpected setback in August when John, whom Farnese had already re-joined with his troops, attacked the States Army camp at Rijmenam, near Tienen. The States troops, led by the Count of Bossu, repelled the attack and moved into the offensive, retaking Aarschot, Nivelle and Jemappes. The arrival of the French army under Anjou further worsened the Spanish situation, as it seized Maubeuge, Roeulx, Soignies and Havré, in Hainaut. The imminent arrival of John Casimir's German army led John to retreat back to Namur and entrench his army in a camp at Bouge, in a height between the Sambre and Meuse rivers. There he fell ill from typhoid fever and died on 1 October 1578. According to Ottavio Gonzaga, 'even the stones mourned him', as he was very popular among his men, while Captain Alonso Vázquez noted that even the German mercenaries were saddened. Farnese, his uncle – though they had similar ages, being on their early thirties – and confidant, accepted the appointment of Governor-General by Don John on his death bed until Philip II finalized it. His main concern was to prevent the Catholic Walloon nobility from forging a solid alliance with Anjou.
In November 1578, as the Spanish army was being decimated by diseases, Farnese left the camp at Bouge garrisoned by just six companies and advanced along the right bank of the Meuse with the bulk of the army, then numbering 20,000 men, towards Limburg. He intended to relieve Deventer, which was under siege by a States Army, but its German garrison surrendered before he could send reinforcements. He then encamped his army between Maastricht and Dalhem and began to conceive the siege of the former city. Before that, to isolate Maastricht from Aachen, Cologne and Cleves, a force under Mondragón was sent to capture the towns of Kerpen and Erkelenz on 31 December. Kerpen was invested on 7 January 1579 and taken four days later. The States defenders were executed, which prompted Erkelenz and Geldern to surrender. Then Mondragón sent 500 infantry and 50 horse to capture Straelen, while another force under Pedro de Toledo was dispatched to relieve the Bleijenbeek Castle, whose lord, Maarten Shenk, had declared for the Spanish. While the States troops were driven away, Mondragón completed the Spanish control of the right bank of the Meuse by taking Valkenburg, Wittem and 's-Hertogenrade.