Fortress Europe- European Fortifications Of World War II
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Norway's situation was different because it built forts in 1905 to protect itself against a possible Swedish invasion before their secession. Three old border forts were modernized and six new ones were erected. They were armed with modern 120-mm, 105-mm, and 75-mm guns ordered from Schneider and placed in turrets or behind armored shields. The border areas of Orje/Urskog and Kongsvinger received two new forts apiece. The older updated forts were located in the Halden area, near the coast. When the union between Norway and Sweden was dissolved later in 1905, the creation of the 20 km neutral zone forced Norway to disarm or destroy the forts that lay within it. Only the forts of Gullbekkasen and Vardasen in the Kongsvinger area had remained in service, and the treaty forbade their modern ization. Forts Orjekollen and Urskog were destroyed and their 105-mm guns placed in storage for future use. However, within a short period of time, new forts went up on the edge of the neutral zone.
In 1907, the Norwegian government ordered the construction of Fort Greaker and the Ravneberget Battery of the Sarpsborg Fortress behind the old Halden position, which were completed in 1910. Fort Greaker received the 120-mm gun turrets from one of the forts destroyed at Halden, and Battery Ravneberget two 105-mm Schneider cannons from old Fort Urskog. The other two guns of Fort Urskog were sent to the Forhlten coastal battery, located between Harstad and Narvik. However they were not yet mounted in 1940.
Two forts were built in central Norway along the border between 1908 and 1910 to cover the two routes leading from Sweden into Norway, east of Trondheim. The unusual Fort Verdal, built into a mountain, included guns mounted in caverns. The most famous of the Norwegian forts was Fort Hegra, guarding the route south of Verdal, directly east of Trondheim.' Its two batteries, only protected by armored shields, like the other inland forts, were set up to face east, against Sweden, a common problem with Norwegian border forts. Battery positions were also set up near the Glomma River, on the main road between Oslo and Stockholm. The construction of three more forts was authorized in 1910, but only the forts of Hoytorp and Trogstad were actually built. When they were completed at the end of World War I, they became part of the Fossum Fortress along with a number of blockhouses and galleries for machine guns that covered the bridges across the Glomma River at Fossum.
Most of Norway's effort was oriented towards coastal defense. The Norwegian coast line was divided into three Sea Defense Sectors to which fortress areas were attached in 1934 when the Coast Artillery was integrated into the navy.' Most of the major cities and assembly areas for the army's half dozen divisions were located in the Sea Defense Sectors.
Most of Norway's fortifications dated from the latter part of the nineteenth century. The famous Oscarsborg fortress on the Drobak narrows was an old position completed in 1856 and modernized in the 1870s and 1890s. It guarded the approaches to Oslo on the Oslo Fjord. The old Carl Johans Vaern Navy Base at Horten was defended by two forts completed in 1859 and modernized in the 1870s. In 1890 the Norwegian government undertook a major effort of modernization when it ordered a three-gun battery of 280-mm Krupp cannons for Oscarsborg.
In 1891, a defense committee selected twenty-one areas to be fortified, but only the Oscarsborg Fortress, the Tonsberg Fortress defending the Melsomvik Naval Base, the Kristiansand Fortress, the Bergen Fortress, and the Agdenes Fortress guarding the approaches to Trondheim, were actually renovated. The government ordered weapons from Great Britain, France, and Belgium and Krupp naval guns for some of the batteries from Germany. Fortress Oscarsborg and Bergen also received a torpedo battery apiece. The one at Oscarsborg was below the water line and that at Fort Kvarven in Bergen was the standard above water unit.
Norway did not attempt to improve its coastal positions until the outbreak of World War I, when two new forts were built on the islands of Raur y and Bolaerne at the mouth of the Oslo Fjord. Plans were made for a battery at Ofot Fjord, near Narvik in the far north. The new weapons were ordered from Bofors in Sweden and Bethlehem Steel in the U.S. However, by the time they were delivered, the war was over, so they went into storage. There followed another period of inactivity that lasted until the 1930s, when it was decided to improve the defenses of Oslo Fjord. At that time, the forts of Rauey and Bolaerne were armed with 150-mm Bofors guns. Work also began on Fort Makerey that received two 305-mm Bofors coastal defense howitzers, and Fort Torars likewise.
Meanwhile, new plans were drawn up for relocating the batteries of Kristiansand and Bergen, and adding batteries and forts at the latter. The two new forts at Bergen, still under construction when the war began, were slated to include a 150-mm gun battery.; Work on these positions was not completed by 1939 nor were the forts protecting the approaches to Narvik.
After World War I, Sweden found itself as the major power in Scandinavia thanks to its modest fleet of coastal defense ships, but it did not pursue a policy of expansion. Thus it failed to seize the opportunity to annex the Aland Islands during the civil war in Finland. Its army was reduced after the war but its navy was kept intact.
The town of Boden, near the Gulf of Bothnia, sat on the rail line connecting the iron mines of Gallivare to the port of Lulea. Soon Boden developed into one of the country's largest rail centers. Fortifications were built there before the turn of the century to protect the region and its iron mines. In addition, the decision to create the fortress zone at Boden was made in 1900 by the Swedish Parliament only six years after the railroad reached the town from Stockholm.
The blasting and excavation work for Fort Gammelang on Mount Svedje, to the east of Boden, and four more large forts began in 1901. All were completed by 1912. Between 1901 and World War I, the army built and occupied more than twice as many smaller works in the intervals. The first gun was installed in 1906 and the first test shot was fired in 1907. Stone barracks for the fortress garrison of Boden were built between 1902 and 1912, replacing the original brick structures. The stone for their construction was quarried from the sites of the forts. More forts had been planned, but the increasing construction costs only allowed the first group to be built. If the large forts had not been built at the same time, some would have not been erected at all. Between the wars, the forts were modernized, receiving electricity, ventilation, heating, and communication lines.
Sweden spread misinformation about Boden in order to discourage foreign incursions from Finland-part of Russia before 1918-and Norway. Although it kept the defenses of the Boden area secret, i t leaked enough information in the 1920s to convince potential enemies that the fortress ring consisted of at least four mountain forts located at Mjosjobergt, Aberget, and Paglaberget. These forts were compared to the forts of Verdun and touted to be much stronger because they had been blasted into the granite rather than soft earth, and had enough protection to resist the type of bombardments witnessed in 1916. Foreign intelligence officers expressed the belief that they compared to the forts of Metz. It was claimed that their armament consisted of 210-mm mortars or possibly howitzers.
After the turn of the century, Sweden concentrated its defensive effort around designated coastal fortress areas at Vaxholm-which protected Stockholm-at Karlskrona in the southeast, at Helsingborg and the narrows between Sweden and Denmark, at Goteborg with Fort Oscar II on the Kattegat, and on the island of Gotland. Many of the guns were mounted on barbette mounts and a few in turrets. However, a number of large caliber weapons, such as 305-mm and 240-mm, became outdated between the world wars or simply wore out. Additional up-to-date 210-mm guns, used on newer warships, were set up late in the 1930s on the islands of Gotland and Karlskrona.
Between the wars Sweden became a major arms producer and concentrated at first on export rather than local consumption. The Bofors works signed an agreement to produce weapons for Germany and other nations. These contracts helped develop the Swedish arms industry to such an extent that by 1939 it was able to produce many of the weapons needed for home defense. In addition, after World War I, Krupp established the Landsverk company in Sweden which produced weapons for export.
Between July and September 1939, the Swedish army completed 267 bunkers during the first phase of construction of the Per Albin line, today known as the Scandia Line. This was done against the wishes of Prime Minister Per Albin Hansson, its namesake! The line was built in four phases: the second phase, when another 124 bunkers were built, lasted from December 1939 to April 1940; the third phase, which continued from April to June 1940, saw the completion of another 527 bunkers; and finally the fourth phase, which extended from June until October 1940, saw the addition of 145 more bunkers. The line spanned the southern tip of Sweden from a point south of Halmstad to a point west of Karlskrona near Ronneby, covering over 350 km. Most of the bunkers were for machine guns, but some mounted anti-tank guns. The coast in this area was open to an invasion staged froom northern Germany or the nearby Danish islands of Sjaelland and Bornholm.
After the German invasion of Norway smaller defensive lines were set up at a dozen road sites on the Norwegian border. These included mostly machine gun bunkers and shelters using the rough terrain's defensive advantages.
When the war began, the Swedish navy consisted of three coastal battleshipswhich had been modernized before the war and given 11.14-inch guns-a few older coastal ships with 210-mm and 150-mm guns, and a light cruiser with 150-mm guns. Naval squadrons operated from bases at Stockholm, Goteborg, Karlskrona, Malmo, and Visby (island of Gotland) that were close enough to support the coastal defenses in their area. However, with only nine modern coastal submarines and a few destroyers, the navy's ability to repel an invasion was limited. The Royal Coast Artillery fell under naval command for the defense of the key bases.
DESCRIPTION
1. Danish Coastal Defenses
The most interesting Danish fortifications were the island forts such as the Flak Fort at Saltholm island, Fort Dragr, r, and Fort Middelgrunds, protected by lagoons formed by jetties. Fort Dragor, at Copenhagen, and nearby Fort Taarbaek mounted mostly older models of heavy artillery. In fact, most of Denmark's ordnance was of World War I vintage or older, ranging from the 305-mm, 170-mm, and 120-mm gun batteries at Fort Middelgrund to the 355-mm gun battery at Fort Drager. The Flak Fort, which had some of the newer weapons, housed 290mm howitzers and 210-mm cannons from the World War I period. Most of the guns were mounted on barbette carriages and protected by armored shields and earthen ramparts. The ammunition and barracks areas were under concrete. Though old, the guns of these coastal defense batteries could be quite effective in the narrow waters of Denmark.
Most of Denmark's coast defenses were clustered in the vicinity of Copenhagen. The Flak Fort was built just north of the island of Saltholm on the Oresund, the body of water separating Sealand from Sweden. The Kongelund Battery, on the southern end of the Copenhagen Fortress, was armed with four 150-mm Bofors guns in 1939 taken from the old coastal battleship Herluf Trolle.
2. Norwegian Coastal Defenses and Forts
The defenses of Oslo Fjord rank as the most important in Norway. Fortress Oscarsborg, located on the Kaholmen Islands and dating back to 1856, received its first "modern" piece of artillery, a breech loaded Krupp 305-mm gun, in 1879. The main battery of three 280-mm M.1889 guns was created in 1893. At the turn of the century, a torpedo battery of 450-mm Whitehead torpedoes was set up on North Kaholmen Island. This battery was cut into the rock and the tubes were underwater. The excavated central rock chamber included complete facilities including torpedo magazines, usine, rest area, etc. There were three fan shaped launching tunnels for torpedoes below this area. The torpedoes were lowered down a shaft into the position from which they were launched underwater on a platform that could traverse twenty degrees. They were not "fired" as in a standard torpedo tube, but moved on their own power through the tunnels.
The fortress also included four British Whitworth 280-mm M.1891 howitzers which formed a battery on Haoya Island, near the Kaholmen Islands. On Haeya Island eight 120-mm guns formed the Lower Top Battery and two newer 120-mm guns M.99 the Upper Top Battery. Anti-aircraft guns were added during World War 1. The battery positions, consisting of masonry and concrete defenses for the guns, lacked overhead protection against air-attacks.
Formerly known as the Topdalsfjord Fortress, Kristiansand Fortress was built at the end of the last century. Its key points were Fort Odderoya and Gleodden Point, whose battery covered the Skagerak. Little was done to modify Kristiansand Fortress between the wars, although plans had been prepared to shift the batteries away from the town. The Main Battery consisted of 210-mm guns supported by three batteries of 150-mm guns (East, Center and West Batteries). The shore battery consisted of 65-mm cannons and a howitzer battery for support. Machine guns constituted the only air defenses. Kristiansand Fortress consisted of:
The Bergen Fortress consisted of an inner and an outer ring, which were authorized in 1895 to replace the obsolete existing fortifications. The main forts and batteries occupied the inner ring that was located close to the city. The outer ring consisted of battery positions that protected the minefield blocking the approaches to Bergen. In 1940, the batteries of the outer ring were turned into small forts. In addition to the weapons listed below, some of the Bergen forts received field pieces in 1939. Fort Kvarven was equipped with two 110-cm searchlights and Hellen with one. The forts of the outer ring had a 90-cm and a 110-cm searchlight apiece.'
The defenses of Trondheim Fjord centered on the Agdenes Fortress. The condition of the weapons in these forts was reported to be deplorable in 1940.
Work was underway on a pair of forts on the entrance to the fjord leading to Narvik, but neither was ready in 1940.
All the frontier forts built after 1905 included subterranean casernes and magazines linked to the combat positions by tunnels. Many of the weapons were put in open positions and had only gun shields for protection.
The two main Norwegian forts on the Glommas Line were armed with a variety of weapons. In 1923 forts Hoytorp and Trogstad received two single 120-mm howitzer turrets that mounted a modified Cockerill field piece.6 They were given two additional 75-mm Cockerill guns in one-gun turrets apiece between 1934 and 1935 to augment the firepower of their two older Schneider-Canet 120-mm turret guns. The four 120-mm single-gun turrets were transferred to forts Hoytorp and Trogstad from the four forts of the old Fredriksten Fortress after World War I. At Fort Hoytorp there were also four old Schneider 120-mm fortress howitzers in gun pits, eight 84-mm field guns, and lighter weapons. German 75-mm Rheinische guns were added to this arsenal between the wars. Fort Trogstad had two turrets with modified 120-mm Rheinische howitzers.
Both Fort Hoytorp and Trogstad had measured about 400 meters in length and 300 meters at the widest part. Their artillery was clustered in different sections of the forts. At Hoytorp all four gun turrets were grouped in a citadel-like position on the northeast side, protected by infantry and machine gun positions and barbed wire obstacles. On the south side of the fort was the 84-mm gun battery, and just north was the 120-mm howitzer battery.
Further north, Fort Hegra guarded the border with a battery of two 75-mm Schneider Cannons and a battery of four 105-mm Schneider guns that were installed in 1910. The 105-mm guns came from the Fort Orjekollen when it was destroyed earlier in the century. Like most of the Norwegian forts, this hilltop fort occupied a strong position but lacked turrets and was oriented towards border defense. The mountain fort of Verdal mounted one 75-mm gun and two 84-mm guns in caverns.
The frontier forts of Vardasen and Gullbekkasen served little purpose, especially when Sweden ceased to pose a threat. In 1939, their two 120-mm guns were relocated to Bergen to form a battery at Fort Leroy.
3. Swedish Coastal Defenses and Fortress Boden
The Swedish defenses, which consisted of a mixture of old and new works, were the most modern of the Scandinavian nations. Some positions like those at Vaxholm, and at Goteborg, were equipped with old 150-mm gun armored turrets. Fort Vastra Hastholms at Karlskrona, and Byviksfortet at Oscar-Fredriksborg (near Vaxholm), mounted 120-mm cannons. The obsolete 240-mm guns on barbette mounts at Fort Oscar II and at Oscar-Fredriksborg were modified and moved to coastal positions in the southeast, where their poor range was sufficient.