The three principal bastions were named the Schottenburg, Moses' Table, and the Flamenburg, the last-named defending the entrance to the Geule on the eastern side. There was a strong wall with three bastions, the North Bulwark, the East Bulwark or Pekell, and the Spanish Bulwark at the south-east angle, with an outwork called the Spanish Half-moon on the other side of the Geule. The south side was similarly defended by a wall with four strong bastions, while beyond these at the south-west corner lay a field called the Polder, extending to the point where the Yper-Leet ran into the ditches.

Sir Francis Vere's first step after his arrival was to throw up three redoubts to strengthen the wall round this field, as had the enemy taken possession of it they might have set the windmills upon it to work and have drained out many of the ditches. Having secured this point he cut a passage to the sea between the North-west Bulwark and the Flamenburg Fort, so that shipping might enter the port without having to ascend the Geule, exposed to the fire of the Spanish guns. To annoy the enemy and draw them away from the vital point near the sea, he then stationed 200 men on some rising ground surrounded by swamps and ditches at some distance to the south of the city, and from here they were able to open fire on the enemy's boats coming with supplies from Bruges.