[3] The city was then merged with the surrounding district and the transition to the new Protestant regime was followed by the expulsion of all property of the Roman Catholics as well as a complete ban on Catholicism.

Pensionary Johan van Oldebarneveldt was thereby prepared to agree to a solution where Groningen would be recognized as a free city under the formal protection of the Duke of Brunswick and even proposed some religious freedom to Catholics.

The talks broke down as the military, in particular the Dutch commander in the region William Louis did not want the Duke of Brunswick as protector, and that Groningen again could easily turn into a repeat of Rennenberg's betrayal.

[6] In preparation for the siege of Groningen, William Louis carefully captured the many sconces that the Spanish troops held, starting in 1589 at the Battle of Zoutkamp, to weaken their hold on the city.

Maurice then ordered William Louis with a detached force to capture the high peat bogs east of Groningen along with the towns of Winschoten and Slochteren, making sure the city was cut off from the German states.

The city however had divided loyalties; the poor were deeply attached to the Catholic faith, but the burghers were concerned about the economy and therefore saw greater advantage with the republic.

Five siege guns were planted against the Drenkelaar tower, ten against the ravelin of the Oosterpoort, twelve against the Heerepoort, six against the Pas Dam, and three against the bastion at the southern angle.

[14] Maurice ordered to stem the water that flowed adjacent with the land – small canals were built to carry his siege guns, and to take the supplies from the surrounding country.

When the guns opened fire there was a steady and continuous reply from the ramparts, and although the Drenkelaar was partially destroyed, and much damage was done to the walls and gates, the defence proved to be stubborn.

[14] A crisis then arose in late May, when Queen Elizabeth ordered the return of her English troops with the need to send them to France because of the Spanish threat on Brest.

[9] Vere acquiesced and asked the Dutch to replace the English troops in the garrisons at Ostend, Flushing, and Briel in order to prevent a collapse of the campaign.

[10] On 3 June, the guns were placed in position opposite the Oosterpoort and Vere had lodged his men within the counterscarp and along the moat, where they were then exposed to gunfire.

In the meantime with this potential news the Spanish garrison fired furiously hoping to weaken the besiegers defences but it only managed to churn up the ground.

[18] The Oosterpoort by mid-June became the main focus of the besiegers cannon fire and the Dutch and English engineers dug mines under the strong ravelin in front of the bastion.

Not long after Maurice and Vere were making a reconnaissance close to the walls, under a large buckler, when a shot struck it, and they were both hurled to the ground but with only minor injuries.

Maurice and his army then paused for a while before launching a campaign in the North East of the Rhine area to retake the cities of Twente, such as Enschede, Oldenzaal, and Lingen.