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Siege of Groenlo
Part of theEighty Years' War and theAnglo–Spanish War
Siege of Groenlo in 1627 by Frederick Henry, including the circumvallation. MapJ.Blaeu.
Date 20 July – 19 August 1627 Location Groenlo,Gelderland (present-dayNetherlands) 52°3′N6°37′E / 52.050°N 6.617°E /52.050; 6.617 Result Anglo-Dutch victory[1]
Belligerents
Dutch Republic England	Spain
Commanders and leaders
Frederick Henry Edward Cecil	Matthijs Dulken (Grol) Hendrik van den Bergh (Spanish Army)
Strength
16,000 infantry 4,000 cavalry	1,200 infantry (Grol) 100 cavalry (Grol) 16,000 infantry (Spanish Army) 5,000 cavalry (Spanish Army)
Casualties and losses
Unknown	Unknown

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Thesiege of Grol in 1627 was a battle between the Army of theDutch Republic, commanded byFrederick Henry, Prince of Orange, and theSpanish-controlled fortified city of Grol (now known asGroenlo), during theEighty Years War and theAnglo–Spanish War in 1627. The Spanish Army, led byHendrik van den Bergh, came to relieve Grol but too late. Thesiege lasted from 20 July until 19 August 1627, resulting in the surrender of the city to the Dutch army.^[2]

During the siege, a 16 kmcircumvallation line was made around Grol to prevent the enemy from leaving and to prevent the liberation of the city from outside.Ambrosio Spinola had used a similar technique during theSiege of Breda (1624), and after the successful siege of Grol Frederic-Henry would later use it in other sieges in the Netherlands, such as at theSiege of 's-Hertogenbosch. The success at Grol provided the first serious victory on land for the Republic after theTwelve Years' Truce.

Even though it was only a small city, Grol was ofmilitary strategic importance. Grol was a flourishingtrade center, wellfortified and armed, and it had a strategic position on theHanseatictrade route toGermany. The area around Grol wasmarshy and difficult to reach, and anyone in control of the city was in control of the region.Maurice of Nassau had taken Grol in 1597, after an unsuccessful try in 1595, andSpinola retook it in 1606. Maurice tried to take Grol again, later during the same year, again unsuccessful, after which Grol remained in Spanish hands until 1627.

Grol provided a defensible place to garrison troops and a freehaven for Spanish raids. Heavy taxes and import duties were collected here from the whole of theAchterhoek andVeluwe, which provided a steady source of income for the Spanish war treasury. Together with the fortified towns ofOldenzaal,Bredevoort andLingen, Grol could provide a base for attacking the republic from the east. AfterOldenzaal had been captured in 1626 byErnest Casimir, theStates-General chose to invest in an army to capture Grol, instead of concentrating solely on sea battles with the Spaniards (which the powerful statesHolland andZeeland wanted).^[3][4]

The Dutch Army of Frederic-Henry, totaling over 15,000footmen and 4,000cavalry, traveled by foot and boat via theRhine and unloaded behindEmmerich. As was common practice in those days, the army consisted mainly ofmercenaries from all overEurope, includingScottish,English,High-German,Frisian andFrench troops. English forces were under the command ofEdward Cecil.^[5] The army arrived at Grol on 20 July 1627. Immediately all major roads leading to Grol were blocked by front runners of the cavalry. 1,000 carts broughtgunpowder,bullets, 75guns, food and all the equipment necessary for besieging and taking over a city.^[6]

The next day, thousands of soldiers and hired workers began to speedily build a continuous earthen wall around Grol, 10 feet high, 16 kilometers long. Wooden and earthenramparts,entrenchments and otherfortifications were built along the line, including fortified defenses for the troops (Dutch:Schansen).

Frederic-Henry used to let troops of the same nationality work together, so that an English fortification (Engelse Schans) was built by and for the English troops, as well as one for the French, the Frisians and one for the troops fromHolland. Guns were placedstrategically so that the circumvallation line could be defended from all sides. The reach of the guns placed in Grol was taken into account: they couldn't hit the line which was 2 kilometers from the city. In just 10 days the work was done, though the circumvallation was continually reinforced during the siege.

Frederic-Henry was aware that a large Spanish army was stationed in the south of the Netherlands, commanded byHendrik van den Bergh. To distract the Spanish army and delay its arrival, and thus avoid a battle in the open field where he would be outnumbered, Frederic-Henry carried out afeigned attack; he sent a part of his own army towards the German town ofGogh. Neighbouring villages around Grol were taken by commanders to prevent the Spanish obtaining a foothold in the neighbourhood. Sentries were placed all around the area and supply lines were set up toDeventer andZutphen, to feed and supply the massive army now lying around Grol.

Matthijs Dulken, a seasoned and wily commander, was the head of the Spanish army occupying Grol. He had available to him 1,200 foot soldiers (not accounting enlisted citizens) and around 100 cavalry, commanded byLambert Verreyken. Food and supplies aplenty, Dulken ordered his troops to reinforce the defenses of the already fortified city, and specifically: "...by musket or cannonball, to hurt or damage the enemy any which way". With the circumvallation line ready, Grol was being bombarded by the Dutch army while groups of Dutch, English, French troops dugsaps towards the city. Damage done to the city's defenses were continually repaired by the besieged. However, 200incendiary "fireballs" were shot into the city, causing heavy damage to buildings and people. Dulken himself was wounded in his shoulder by a musket bullet and gave command to Verreyken. Verreyken and his cavalry raided the attackers positions, mainly the trench digging positions and the rampart ofErnst Casimir of Nassau-Dietz, without causing many casualties. In Grol, due to the carelessness of a soldier, two barrels ofgunpowder exploded, causing forty bystanders to perish.

Meanwhile, the English digging team had managed to first reach thecanal which lay around Grol and was supplied by the river Slinge. In order to facilitate a crossing, thelock north of the city was blown up, resulting in the lowering of the water in the canal by five feet, which left just nine feet. After that, the Dutch army tried to cross the canal by building a dam, but they were under heavy gunfire from Grol and the dam was fully destroyed by burning oil poured from the city. Finally, with the support of two artillery pieces the attackers managed to build two dams, although casualties were great, including two English officers, Ram and Proud. Having crossed the canal, they could now begin to undermine Grol's outer defensive walls, even though regular attacks were made from out of the city.

In the meantime, Van den Bergh and his formidable Spanish army had arrived near Groenlo after taking in another 1,800German mercenaries, now outnumbering the army of his cousin, Frederic Henry. However, due to lack of funding they were short on supplies and had arrived too late for a head-to-head battle in the open field. They fired their guns for Grol to hear that help had come. After a failed plan to cut the supply lines of the Dutch army, due to quarrels between Spanish and Italian troops, he decided to attack the circumvallation line and try to break through to Grol. His attack on the Scottish rampart seemed to succeed at first, but a fierce counterattack by Officer Morre drove the Spaniards away, erasing all hope for a victory for Van den Bergh.

Frederic-Henry now tried to negotiate with Dulken, by convincing him the Spaniards outside the city could no longer save him. Dulken, who had healed from his wound, proudly denied their entreaties. The siege went on. English troops crossed the canal and managed to put a mine under one of Grol's outer defenses (faussebray). The mine was blown up on August 18, creating a huge hole in the defenses. English troops rushed in, climbing the city's earthen walls behind, but Verreyken lay waiting with hundreds of muskets andburning tar, and he repelled the English three times, causing a massacre. Dulken however, intelligent enough in knowing that soon his city would be attacked from three sides, and realizing that he was short on men and guns, called for anarmistice and sent for negotiators.

Atreaty like the one used after thesiege of Breda was signed 3 days later, handing the city to the army of the Republic. The Spanish troops in Grol and its citizens were allowed to leave, taking arms and loot with them, but only 2 guns could be taken. Frederic-Henry loaned 200 carts for the defenders to carry their equipment, as was negotiated. He stationed foot soldiers and horsemen in Grol, as to defend it from future attacks. The complete circumvallation line was destroyed and all trenches filled, to prevent them from being used by future attackers.Archbishop of UtrechtPhilippus Rovenius, who resided in the city during the siege, was allowed to leave. Grol was now under the Republic and would remain so until the end of the war.

The victory was celebrated greatly in the Republic. The Spaniards had finally been beaten after many losses.Hugo de Groot wrote all the details of the battle in his 'Grollae Obsidio' andJoost van den Vondel wrote a 738 verseode to the siege. The sayingZo vaste as Grolle (as sturdy as Grolle) came into being, as a reference to the difficulty of taking the city.

Groenlo, influenced byMunster and having been under SpanishCatholic control during many years, remains a Catholicenclave in a predominantlyProtestant region. Numerous paintings of the siege have been made famous by well known artists of the period

In the town ofGroenlo, old Grol, cannons and some parts of the old bulwarks have been restored for historic andtourism purposes. Livereenactments of the events of 1627 take place on a regular basis, drawing sizable crowds - these are known as the 'Slag om Grolle'. In recent years, more and more parts of the original circumvallation line are being rediscovered. It is being discussed whether the full 16 kilometer long line can be restored. During 2006 and 2007, the (Old) Calixtus church in Groenlo has undergone a major renovation, including the placement of a new stained glass window depicting the siege of Groenlo of 1627. The church has survived all of the six sieges that Groenlo has been through during the 16th and 17th century. After the siege of 1627, the States-General paid for the breaking of a church window that occurred during the siege.

In the hot Dutch summer of 2003, anultralight plane discovered mysteriously green plants in an otherwise barren corn field. It just so happened to be the outlines of the French rampart of 1627 (Franse Schans). The canals around the rampart changed the soil or water flow, making the plants stay green. The English rampart was found earlier nearLievelde and has been fully restored and it can be visited.

The 'Battle of Grolle' is a regularhistorical reenactment of the siege. It is held in and around Groenlo itself every two years. The event lasts for three days and features a historic battle reenactment and a historic fair. The event was held for the first time in 2005, and since then reenactors fromFrance,Germany,United Kingdom, theCzech Republic as well as theNetherlands have taken part. The latest re-enactment was in October 2024.^[7]

• Jaques, Tony (2006).Dictionary of Battles and Sieges: A Guide to 8500 Battles from Antiquity Through the Twenty-first Century. Greenwood Press.ISBN 978-0313335365.

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• Battle for Grolle 2008 (reenactment) (in English)
• Groenlo Vestingstad (in English)

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