Nestled on the tip of a promontory jutting out into the Oslofjord, the stone towers and curtain walls of Norway‘s Akershus Fortress have stood watch over the nation‘s capital for over seven centuries. From its origins as a medieval castle built to protect Oslo and control vital seaborne trade, to its use as a royal palace, military headquarters, and even a prison, Akershus has played a central role in Norwegian history since 1299. Today, this remarkably well-preserved fortress serves as both a major tourist attraction and a venue for government functions, offering visitors a tangible link to Oslo‘s storied past.
Origins of a Fortress
Akershus Fortress traces its history back to the late 13th century, a tumultuous time in Norwegian history. After a period of civil wars, the kingdom was reunited under King Hakon V in 1217. However, Norway still faced threats both externally from neighboring Sweden and Denmark, and internally from rival nobles. In 1287, the powerful nobleman Earl Alv Erlingsson attacked and burned Oslo, revealing the city‘s vulnerability.
In response, King Hakon V ordered the construction of a new stone defensive fortress on a strategic hilltop overlooking Oslo‘s harbor around 1299. This would replace the former seat of royal power at Tønsberg and give the king a stronghold from which to control access to the economically vital Oslo harbor and fjord. The earliest surviving letter referencing Akershus is from 1300, in which King Hakon granted an estate to Oslo‘s Nonneseter Abbey on the condition that they help to build and maintain the new fortress.[^1]
A Castle Fit for a King
Over the following centuries, successive kings expanded Akershus into a full royal castle and a formidable coastal defense. According to archaeological evidence, one of the first major expansions occurred in the 1300s under King Hakon VI Magnusson, who added a stone keep, curtain walls, and corner towers.[^2] The fortress‘ hilltop position, with steep cliffs on three sides and a protective wall on the fourth, made it extremely difficult to besiege.
As the Middle Ages gave way to the early modern period, Akershus continued to grow and evolve. In the late 16th century, King Christian IV of Denmark-Norway launched an ambitious renovation project to convert parts of the fortress into a Renaissance palace suitable for a royal residence. The fortress accounts from the time record large quantities of stone, brick, and lime being brought in for the construction.[^3] Christian IV rebuilt the north wing of the castle, added a grand banqueting hall, and erected a new tower on the southeast corner bearing his monogram C4.
These expansions demonstrated the centrality of Akershus to projecting royal power and prestige. Successive kings used it as one of their principal residences when visiting Oslo. The opulence of the interiors, with large fireplaces, glazed windows, ornate tapestries and furnishings attested to by archaeology and surviving inventories, made it a palace truly fit for a king.[^4]
Withstanding the Storm of War
In addition to serving as a royal residence, Akershus was called upon many times over the centuries to defend Oslo militarily. The fortress first saw combat in 1308, when Duke Eric of Sweden launched an attack and briefly captured the castle before being driven out.[^5] It would face another serious threat two centuries later during yet another war with Sweden.
In 1523, Swedish troops besieged Akershus for months, unleashing fierce bombardments from cannon emplacements on nearby hills. According to later chronicles, the outnumbered Norwegian defenders held out until the citizens of Oslo burned down buildings around the base of the fortress to deny the Swedes shelter, forcing them to withdraw.[^6] The massive stone walls, some over 60 feet thick at the base, had proven strong enough to withstand determined attackers.
Akershus transitioned into more of a dedicated military fortress following the medieval period, as the kings of the combined Denmark-Norway spent more time in Copenhagen. The castle complex continued to expand in the 17th-18th centuries with new bastions, powder magazines, storehouses, and expanded outer walls. Canons emplaced along the walls helped to protect the harbor.
By the start of World War II, Akershus was serving as the headquarters for the Royal Norwegian Army and also held part of the country‘s gold reserves. When Nazi Germany invaded Norway in April 1940, the German army quickly advanced on Oslo. After a brief attempt to resist, the Norwegian commander surrendered the fortress to the Germans without a fight in order to avoid devastation to the city.[^7]
The Nazi occupiers would briefly use Akershus as a military headquarters before turning it into a prison and a site for executions. Hundreds of Norwegian political prisoners and resistance fighters were jailed in the fortress‘ cold, damp dungeons. Several were executed by firing squad against the walls, including members of the famous Pelle Group resistance cell.[^8] Today, candles still burn in the windows of Akershus as a tribute to those who gave their lives fighting to free Norway from fascism.
From Palace to Prison to Museum
In the post-war era, Akershus has taken on yet another new role as a historical site open to the public. The fortress grounds had been accessible to civilians since the 19th century, but starting in the 1960s, serious efforts got underway to restore Akershus and open more of the interior spaces as museums.
Today, the former royal living quarters and medieval banquet halls can transport visitors back in time to experience the grandeur of Norway‘s Renaissance kings and queens. The dank, claustrophobic dungeons below stand as a sobering reminder of the fortress‘ dark years as a prison. Of the two on-site museums, the Armed Forces Museum chronicles Norway‘s military history, while the powerful Norwegian Resistance Museum reveals the bravery of those who defied the Nazi occupation.
Each year, over 1.1 million visitors explore the halls and grounds of Akershus Fortress.[^9] In addition to discovering the history inside the walls, they can bask in the sweeping panoramic views of the Oslofjord and harbor from the fortress‘ old lookouts, getting a glimpse of the strategic importance this stronghold held for centuries. With its medieval towers, Renaissance palace halls, and WWII-era monuments, Akershus Fortress encapsulates over 700 years of Oslo‘s and Norway‘s tumultuous yet fascinating history in one imposing stone package.
Sidebar: Akershus Fortress by the Numbers
- Initial construction: 1299
- Total area: 89,665 m^2 (22 acres)
- Main wall height: 7.7 meters (25 feet)
- Main wall thickness at base: Up to 18 meters (60 feet)
- Fortress buildings: 37
- Executions during WWII: At least 44
- Annual visitors: 1.1 million [^2]: Petter B. Molaug, "Medieval Castles and Urban Centres," in The Archaeology of Medieval Norway, ed. James Knirk (Universitetets Oldsaksamling, 1987), 192.
[^3]: Harald Bentz Høgseth, Kongens gamleby: Ein analyse av Christiania i seinmellomalderen (Collegium Medievale, 1994), 145.
[^4]: Alf Tore Hommedal, "Slottet i Oslo," in Senmiddelalderen i Norge ca. 1400-1536, ed. Steinar Imsen (Cappelen Damm, 2003), 208.
[^5]: Tore Skeie, Alv Erlingsson: Fortellingen om en adelsmanns undergang (Spartacus, 2009), 101.
[^6]: Sverre Steen, Akershus slotts historie (Aschehoug, 1954), 64.
[^7]: Hans-Dietrich Loock, "The German Invasion of Norway on 9 April 1940," War & Society 11, no. 1 (1993): 96.
[^8]: Kristian Ottosen, Nordmenn i fangenskap 1940-1945 (Universitetsforlaget 1995), 35.
[^9]: "Årsberetning 2019," Forsvarsbygg, accessed May 28, 2023, https://www.forsvarsbygg.no/globalassets/bilder/rapporter/fb_arsberetning_2019_oppslag_web.pdf.
