Yesterday Crown Prince Haakon marked the 75th year anniversary of the Operation Gunnerside. The mission, also called the Heavy Water Action was a series of military sabotage against Norsk Hydro’s facility at Rjukan during World War II prevented the Germans from going ahead with their atomic bomb program.

Led by Joachim Rønneberg, the plan was no easy task. Having arrived in the mountains on 16 February, the group was ready to attack the evening of 27 February 1943.

The group voted on one of the three options to be successful with their mission. After contemplating a trek down the mountain which was laden with minefields or the second option of crossing a heavily guarded single lane suspension bridge, the opted for the third choices instead. They would hike to the bottom of the gorge, cross the partially frozen river and then climb a 500-foot high cliff. This option seemed more feasible as the route was not as guarded.

When the finally gained access to the building, Rønneberg and his men placed two strings of explosive charges next to the heavy water production cells. To allow ample time to escape yet still know the charges worked, he shortened the fuses giving them a mere thirty seconds. The group made it out safely, and after hearing the explosion, they knew the mission was a success.

To mark this pivotal milestone in Norwegian history and the history of World War II, Crown Prince Haakon geared up and followed the same path these heroes did back in 1943.

Following the somewhat treacherous trek to the gorge, the Norwegian Royal stressed the importance of marking the action to remind ourselves and younger generations of what their ancestors fought for: “A day like this is about our story, our values, that we should not take our fought freedoms for granted.”

Now 98 years old Rønneberg was not able to make the trip to mark the anniversary. Crown Prince Haakon did record a video that will be sent to this Norwegian hero.

In 2015 Rønneberg told The New York Times: “Getting inside I was quite certain that the rest of the party would follow me, but only one chap came. The other ones hadn’t found the entrance to the tunnel. Therefore we decided we would have to do it ourselves and started laying out the charges.”

Demolished in 1977, the factory had seen a resurgence in interest when the cellar floor was excavated last year raising interest in the site and its history.