[2][3] Håkon V also initiated construction of Norwegian fortresses at Akershus and Vardøhus as part of a broader defensive policy.

Along the inside of the surrounding wall buildings were located which among other things included the 'Kings hall', the castle commander's residence, the chapel, the guardroom, the barracks and the kitchen.

Two men from the garrison volunteered to detonate the tower's magazine, causing a massive explosion (the "Bohus Bang") which killed hundreds of Swedish soldiers and thwarted the attack.

[6] They gave Henrik Gyldenstierne, Captain of Bohus, a ring and a gold chain worth 3,000 Danish dalers.

This construction was one of the early works of Hans van Steenwinckel, also from the Netherlands, who later became noted for his Dutch Renaissance style design in Denmark.

As Swedish invasions continuously threatened Norwegian Båhuslen during this time period, the improvement of the fortifications went on for years.

Under the terms of the Treaty of Roskilde in 1658, Denmark–Norway ceded the Danish provinces of Scania, Blekinge and Halland (the latter was agreed to belong to Sweden for a period of 30 years after the Peace of Brömsebro, but was given to Sweden permanently in the treaty of Roskilde) and the Norwegian provinces Trøndelag and Bohuslän (including the Bohus Fortress).

[8] After an unsuccessful attempt to recapture the fortress in 1676, a Norwegian army under the command of Ulrik Frederik Gyldenløve returned in June 1678 and besieged it again.

The most noted prisoner was the radical pietist Thomas Leopold, who spent 42 years of his life behind bars, 32 of those at Bohus, for his alleged heresies.

A report from the 18th century states this as "a great depth, which has a floor of an iron net, upon which the delinquent has to walk and sleep.

The floor accepts all their faeces, but then returns an unbearable stench, that soon makes the poor prisoner confess whatever crime he has committed".