At the end of the 16th century, Norway was part of Denmark and Christian IV was king. The tolls that Denmark takes in the Öresund brings in a lot of money. Money that he uses to strengthen and rebuild the fortresses around Denmark and Norway.

During the 16th century, cannons have become more effective and stronger walls are now needed. The year is 1588 and King Kristian sends Hans van Steenvinkel, who has just become the official national building contractor, here to Bohus to investigate how the castle can be better fortified. Many of the outer walls that run around the fortress are now being built.

The bastion Skarpe Nord, which we stand on, is part of this extension. The bastions are wide enough to place cannons with small protruding hills at the sides to serve as protection for the artillery soldiers. The bastions sink in some places while others protrude like points so that the enemy can be lured into pockets and can be fired at from several different angles.

If the enemy managed capture an area in the fortress, that spot would become the target to avoid having the enemy being able to take advantage of it. When the siege attempt is over, Bohus prisoners have to repair the walls.