The war was re-kindled later that year, and during just 18 months, the Swedes attacked Halden in three independent campaigns. There was no fortress proper at this point. Just the improvised fortifications from 1644 made from timber and stacked stones. These basic fortifications were reinforced and improved upon between the attacks. The Swedes wanted to take a larger piece of Norway but all attempts were countered with fire from Halden. It is these attacks that are portrayed under the year 1660 of the experience.
Only after the third and fiercest attack and a six week siege during January and February 1660, did King Fredrick III understand the strategic importance of Halden. Its location was the bottleneck where several important connections between Norway and Sweden converged. And the king ordered that very year the construction of a new, modern fortress at this location. We can see the king issuing the decree and the construction plans for the fortress. The construction work on Fredriksten fortress proper started in 1661.
