Siege of Groenlo ( 1627 ) The Siege of Grol in 1627 was a battle between the Army of the Dutch Republic commanded by Frederick Henry , Prince of Orange and the Spanish controlled fortified city of Grol ( now known as Groenlo ) , during the Eighty Years War in 1627 . The Spanish army led by Hendrik van den Bergh came to relieve Grol , but it came too late . The siege lasted from 20 July until 19 August 1627 , resulting in the surrender of the city to the army of the United Provinces . During the siege , a 16 kilometer long circumvallation line was made around Grol in order to prevent the enemy from leaving and to prevent liberation of the city from the outside . Ambrosio Spinola had used a similar technique during the Siege 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 the Siege of ' s - Hertogenbosch . The success at Grol provided the first serious victory on land for the Republic after the Twelve Years ' Truce . About Grol . Even though it was only a small city , Grol was of military strategic importance . Grol was a flourishing trade center , well fortified and armed , and it had a strategic position on the Hanseatic trade route to Germany . The area around Grol was marshy 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 , and Spinola 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 the Achterhoek and Veluwe , which provided a steady source of income for the Spanish war treasury . Together with the fortified towns of Oldenzaal , Bredevoort and Lingen , Grol could provide a base for attacking the republic from the east . This is why the States - General chose to invest in an army to capture Grol , instead of concentrating solely on sea battle with the Spaniards ( which the powerful states Holland and Zeeland wanted ) . Prelude . The Dutch Army of Frederic - Henry , totaling over 15 , 000 footmen and 4 , 000 cavalry , traveled by foot and boat via the Rhine and unloaded behind Emmerich . As was common practice in those days , the army consisted mainly of mercenaries from all over Europe , including Scottish , English , High - German , Frisian and French troops . The army arrived at Grol on the 20th of July 1627 . Immediately all major roads leading to Grol were blocked by front runners of the cavalry . 1 , 000 carts brought gunpowder , bullet s , 75 gun s , food and all the equipment necessary for besieging and taking over a city . Circumvallation . 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 earthen rampart s , entrenchment s and other fortification s were built along the line , including fortified defenses for the troops ( ) . < br > 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 from Holland . Guns were placed strategically 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 . < br > Frederic - Henry was aware that a large Spanish Army was stationed in the south of the Netherlands , commanded by Hendrik van den Bergh . To distract and delay the arrival of the Spanish army , and thus avoid a battle in the open field where he would be outnumbered , Frederic - Henry carried out a feigned attack : he sent a part of his own army towards the German town of Gogh . Neighbouring villages around Grol were taken by commanders to prevent the Spanish getting foothold in the neighbourhood . Sentries were placed all around the area and supply lines were set up to Deventer and Zutphen , to feed and supply the massive army now lying around Grol . The Siege . The situation in 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 by Lambert 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 dug " approches " ( zigzag ging trench es ) towards the city . Damage done to the city ' s defenses were continually repaired by the besieged . However , 200 incendiary " 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 of Ernst Casimir of Nassau - Dietz , without causing many casualties . In Grol , due to the carelessness of a soldier , two barrels of gunpowder exploded , causing forty bystanders to perish . Activities outside Grol . Meanwhile , the English digging team had managed to first reach the canal which lay around Grol and was supplied by the river Slinge . In order to facilitate a crossing , the lock 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 . The arrival of Van den Bergh . In the meantime , Van den Bergh and his formidable Spanish army had arrived near Groenlo after taking in another 1 , 800 German 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 . Negotiations . 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 and burning 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 an armistice and sent for negotiators . The Treaty . A treaty like the one used after the Siege 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 Utrecht Philippus 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 ' and Joost van den Vondel wrote a 738 verse ode to the siege . The saying " Zo vaste as Grolle " ( as sturdy as Grolle ) came into being , as a reference to the difficulty of taking the city . Present day . In the town of Groenlo , old Grol , cannons and some parts of the old bulwarks have been restored for historic and tourism purposes . Live reenactment s 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 . < br > 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 . < br > In the hot Dutch summer of 2003 , an ultralight 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 near Lievelde and has been fully restored and it can be visited . In 2008 , the Siege of Grol will be reenacted from 17 until 19 October . < br > Groenlo , influenced by Munster and having been under Spanish Catholic control during many years , remains a Catholic enclave in a predominantly Protestant region .