Course
After the secret Treaty of Dover between France, England, the Prince-Bishop of Münster and the Archbishop of Cologne against the Dutch Republic, French troops passed through the possessions of Münster and Cologne and a few other French allies then the Spanish Netherlands, enabling them to by-pass the Dutch defences in the south and invade the Dutch from the east in June. Bernhard von Galen, bishop of Münster, invaded the Netherlands on 1 June 1672 in several places, taking several towns (including Enschede, Almelo and Borculo) and laying siege to Groenlo, where his forces were joined by those of France and Cologne.
Groenlo was well-supplied with food, garrisoned with 22 cannon on new gun-carriages and 600 troops (made up of 10 infantry companies and 1 cavalry company, led by the infantry lieutenant-colonel Gustaff Tungel) and defended by bulwarks and a moat (which had proved their effectiveness in a 1627 siege). However, vastly outnumbered by the French force of over 100,000, it was only able to hold out for 10 days, after which the besiegers moved onto Deventer and other cities, in what became the 'Rampjaar' for the Dutch Republic. The most important parts of Groenlo's fortifications were demolished by the Bishop of Münster and his occupying troops only left the town in 1674.
Read more about this topic: Siege Of Groenlo (1672)