Theres a long story about the fortress and after the Swedish-Norwegian union where disolved in 1905 Norway accepted to demolish the border fortifications and establish a demilitarized zone along its borders against Sweden.
A new defence line where planned and in the years from 1905 to 1915 several defence positions where constructed along the border and Høytorp fortress became main fortification for a line of defences along the river Glomma.
Early morning 9th of april 1940 Norway was invaded by German forces.
The Norwegian coastal fortification “Oscarborg” in Drøbak spotted and attacked German heavy cruiser “Blücher” on sight same morning with the result of Blücher sinking and over 1000 Germans died.
The following day, 10th of april German infantery began unloading from Oslo harbor and on the 11th General Nikolaus Von Falkenhorst gave the order to begin the offencive operation and advance and hold Norwegian soil.
One infantery regiment where sent into region of Østfold supported by an infantery batalion who where sent to Lillestrøm.
Using confiscated trucks and busses the infantery regiment moving towards Askim reached Spydeberg (other side of the river) arround 0700 12th of April.
Meanwhile IR1 – Infantery Regiment 1 and three batteries from AR1 (Artillery Regiment 1) had grouped up in Askim and divided its forces to secure the disctrict. The three powerplants at Vamma, Kykkelsrud and Solbergfoss was secured aswell as the bridge at Fossum and railway bridge at Langnes.
With Fossum bridge being the most likely place to cross the river the mainforce of about 120 infanterymen plus 9 officers lead by captain Fredrik Solie where given the task of secure the bridge.
Arround 0700 on 12th of april the German advance force arrived in busses at Fossum and went straight into an ambush setup by the Norwegian forces at place.
The first two busses where totally demolished by the massive fire from 8 machineguns with fatal result for the German forces in them.
The bridge where rigged to be blown up but unfortunately the main charge didnt go off and one of the enginer sergeants ran out in middle of the crossfire to set fire to the second charge. This charge was however not big enough to blow up the entire bridge.
For few hours combat raged on until German soldiers where spotted trying to cross the river on the ice. Captain Solie rang Solbergfoss powerplant and ordered them to open the floodgates imidiately which resulted in the ice breaking up where the German soldiers where and alot of them drowning.
Several events later, Norwegian forces got reinforcements from about 60 new men.
Few hours after midnight Germans started a massiv attack on the Norwegian forces using parachute flares to light up the Norwegian positions.
After a while they managed to get some soldiers over to the east side and established a position from where they could flank the Norwegian soldiers.
Few hours later the Norwegian forces where overrun and several Norwegians where injured and with 15 dead men of the total 129.
The Norwegian forces had regrouped about 2,5km east of the bridge with a rifle company and 5 machineguns. The rifle company tried a counter attack but where quickly pushed back by German mortars and machineguns.
After loosing four new men and more wounded they withdraw to Langnes area.
At 12:40 the orders came to reorganize at Korsegård and Sekkelsten east of Askim.
Meanwhile German forces where moving through Askim town and shot at anything that moved with the result 12 civilians where killed and many more injured.
Withdrawing to east side of Askim ment the following German forces now came within reach of the cannon batteries at Høytorp fortress and Trøgstad Fortress.
Directional fire using phone worked for a while until the Germans disabled the phone central in Askim which broke the connection to the fortresses.
This didnt stop fortress Høytorp which continued to fire using their maps, focusing the fire on road junctions, roads and other possible locations.
Afternoon of 13th april general Carl Johan Erichsen ordered the five new 12cm cannons moved to Sweden to avoid them getting caught by German forces. Along with this about 400 men from Høytorp fortress followed out reducing the amount of troops at the fortress.
Høytorp fortress was now in a problematic situation with not enough men to defend it properly and out of ammunition.
Commander Lauritz Rodtwitt who where in charge of the fortress ordered his about 300 remaining men to secure and hold the fortress aslong as possible, by moving them into the reduit (inner circle of the fortress).
The German forces quickly sourrounded the fortress but each attempt of storming it ended in losses.
On the morning of 14th april German planes started attacking the fortress from above which was mentaly challenging for the Norwegian soldiers within the fortress.
Low on ammunition, high risk for the men Rodtwitt desided it was tacticaly wise to abandon the fortress to avoid further cassaulties.
Fortress Høytorp now functions as a recreational area, museum and meeting place for the locals and visitors. Theres during summertime possible to get guided tours through the tunnel system within the fortress and its small museum.
Every year a group of ww2 era entusiasts holds a meeting there for those that have or is interested in ww2 equipment mainly vehicles but also uniforms and other effects from that era.