Danevirke The Danevirke ( modern Danish spelling : Dannevirke ; in Old Norse ; " Danavirki " , in German ; " Danewerk " ) is a system of Danish fortifications in Schleswig - Holstein . This important linear defensive earthwork was constructed across the neck of the Cimbrian peninsula during Denmark ' s Viking Age . It was last used for military purposes in 1864 . The Danevirke stretches for 30 km , from the marshes in the west of the peninsula to the town of Schleswig , which lies beside the Schlei ( Danish : " Slien " ) on the Baltic Sea coast , near the former Viking trade centre of Hedeby . Another wall , between the Schlei and the town of Eckernförde , defended the Schwansen peninsula . According to written sources , work on the Danevirke was started by the Danish King Gudfred in 808 . Fearing an invasion by the Franks , who had conquered heathen Frisia over the previous 100 years and Old Saxony in 772 to 804 , Godfred began work on an enormous structure to defend his realm , separating the Jutland peninsula from the northern extent of the Frankish empire . Carbon - 14 dating however dates the initial construction to be in the second half of the 7th century , and Dendrochronology suggests that construction began not very long after 737 ( a few decades before the reign of Gudfred ) . New Carbon - 14 dating in 2013 has revealed that the second stage started in the years around 500 AD , and the oldest fortification are even older than that . Archaeological record . Archaeological excavations in 1969 – 75 established , with the help of dendrochronology , that the main structure of the Danevirke had been built in three phases between AD 737 and 968 . It is , therefore , contemporary with Offa ' s Dyke , another great defensive structure of the late 8th century . Recent investigations suggest that Danevirke was not only and not primarily built for military purposes . The archeologist Henning Hellmuth Andersen found that in an early stage the main " wall " consisted of a ditch between two low embankments . The historian argued that the " Kograben " ( Danish : Kovirke ) south of the main wall consists of an embankment accompanied by a ditch on its northern side , which would have been counterproductive for a Danish fortification . So the main wall , in its earliest stage , and the " Kograben " rather would have been shipping canals . The shortcut between Baltic Sea and North Sea via Schlei in the east and Treene and Eider in the west was understood previously , but historians believed that boats had been moved on rollers between the Schlei and Treene . See Portage . An excavation in 2009 – 10 stonewall near Dannevirke Museum west of the town of Schleswig Dannevirke so far only port ( Kalegat or Viglesport ) was found , where Hærvejen crosses the rampart . Size . The Danevirke is about 30 km long overall , with a height varying between 3 . 6 and 6 m . During the Middle Ages , the structure was reinforced with palisade s and masonry walls , and was used by Danish kings as a gathering point for Danish military excursions , including a series of crusader raids against the Slavs of the south Baltic . In particular , the 12th - century King Valdemar the Great reinforced parts of the Danevirke with a brick wall , which enabled a continued military use of the strategically important structure . The reinforced parts of the structure are consequently known in Danish as " Valdemarsmuren " ( " Valdemar ' s wall " ) . Symbolism . During the prolonged nineteenth century political and military struggles between Danes and Germans over possession of the territory variously known as " Sønderjylland " or " Slesvig " by the Danes and " Schleswig " by the Germans , the Danevirke was used as a potent symbol of Danish nationalism . Specifically , it was a symbol of the Danish historical claim for the whole of this territory — although during the centuries since its construction the linguistic frontier has moved gradually northwards , so that in the 19th century the territory north as far as Flensburg as well as south of the Danevirke was predominantly German - speaking . The fiefdom remained as a Danish fief . Second War of Schleswig . The last military use of the Danevirke was during the Second War of Schleswig in 1864 . Due especially to the above - mentioned emotive nationalist symbolism , public opinion in Denmark had expected the coming battle to take place here , and the Danevirke was already under attack , although no battle took place there ( except some early skirmish ing near south of it ) , as the Danish Commander in Chief , General de Meza , withdrew to the trenches at Dybbøl due to threat of being outflanked , as the Schlei and the wetland s between the Danevirke and Husum had frozen solid in a hard winter ; also , the territory immediately in front of the Danevirke had already fallen into German hands . This retreat came as a surprise to the Austro - Prussian army , and almost all of the Danish army succeeded in completing the evacuation . It resulted , however , in the abandonment of important pieces of heavy artillery , and it remains a matter of historical debate why the railway to Flensburg was never properly used for the evacuation . News of the retreat came as a great shock to Danish public opinion which had considered the Danevirke to be impregnable , and General de Meza was promptly relieved of his command . The Danevirke has remained in German possession ever since . Stages in the building of the Danevirke . Danevirke 1 — Hovedvolden ( " the main rampart " ) , Nordvolden ( " the north rampart " ) , Østervolden ( " the east rampart " ) The first Danevirke was built in five stages , starting about 650 , according to carbon - 14 dating . The first three stages were simple ramparts of soil , and the fourth stage was a palisade rampart with heavy timber front , build in 737 . In the final stages the timber palisade was reinforced with a heavy stone wall around the timber . Work said to have been started by Angantyr , and continued by Siegfried , and ended by Guðfrið according to annales in 808 . Danevirke 2 — Kovirke ( " cow - work " ) / Kograben ( " cow - moat " or " district moat " ) Built either by Guðfrið or by Harald Bluetooth ( if it is the work mentioned as newly made in the Frankish royal annals in 808 , then Harald did not build it ) it stretched from the Rheide Å about 7 km to a southern extension of the Schlei bay which is now a lake called Selker Noor . Its palisade was about 3 m high , and was a little more solid than that on the first ramparts . The bank of earth behind the palisade was about 2 m high and 7 m wide . It had a V - shaped moat , 4 m wide and 3 m deep . The construction period of this rampart should be some time between 770 and 970 . Danevirke 3 — Hovedvolden / Hauptwall / " main rampart " , Krumvolden / Krummwall / " curved rampart " , Buevolden / Bogenwall / " bow rampart " ) , Dobbeltvolden / Doppelwall / " double rampart " , Forbindelsesvolden ( " the connecting rampart " ) / Margarethenwall ( " Margret ' s rampart " ) Hovedvolden was expanded , so that it was now about 5 m high and about 20 m wide . Krumvolden was built through the Rheide Å , and overlapped with Hovedvolden . Forbindelsesvolden closed a gap between Halvkredsvolden ( " the semicircle rampart " , a bank that protected Hedeby ) and Hovedvolden near Dannevirke Sø . Buevolden and Dobbeltvolden protected an important road junction . This wall is connected to most of the building work is attributed to Harald Bluetooth . Arild Hvitfeldt ' s " Danmarks Riges Krønike " adds a little detail to the extension of the Danevirke in that time period . " Then summoned ( Queen ) Thyra ( wife of Gorm the Old ) Danes from all the kingdom ' s regions to meet at the border and under her supervision they built a wall of earth and timber from Slien over the moors to Trene . The men of Skåne received the western section from Karlegat to Trene . Zealanders and Funen dwellers received the section east from Slien ( Schlei bay ) to Karlegat . Jutlanders provided provisions to the whole army . " This would place Thyra ' s extension sometime before 940 . Forbindelsesvolden was attacked by Germans in 974 . Danevirke 4 — Hovedvolden / Hauptwall / " main rampart " . Reinforcement on the Main Wall finished in 954 , and a new Forbindelsevold build from 964 to 968 . Harald Bluetooth is thought to be the main constructor . Danevirke 5 — Forbindelsesvolden , Krumvolden , and Hovedvolden Under Canute IV of Denmark ( 1080 – 86 ) Denmark was at war with the German empire . The Danevirke was strengthened at the beginning of the 12th century : the moats were deepened and the ramparts were made higher . A granite boulder palisade wall was built on a part of Hovedvolden . Danevirke 6 — Hovedvolden and Thyraborg Valdemar I fortified the rest of Hovedvolden with the famous " Valdemar - wall " , a 7 - m high wall of stones in mortar on a granite boulder base , propped up with buttresses and covered with tiles . This was a large reinforcement , and doubtless deterred many who tried to send an army northwards through Jutland . It was the last true reinforcement of the ramparts . Later Thyraborg castle was built . The Danevirke began to lose its purpose in the 14th century , owing both to the expense of manning it and to the development of ballista s , trebuchet s , and similar siege engines . The Danevirke in World War II . Following the Allied invasion of Normandy during World War II , the Wehrmacht feared that a second Allied invasion might take place through Denmark , and contemplated converting the earthen wall into an anti - tank trench to counter this threat . Had the proposal been implemented , it would have destroyed the structure . Hearing of the plans , Danish archaeologist Søren Telling — aware that all archaeological investigation was under the ultimate jurisdiction of SS chief Heinrich Himmler — immediately telephoned both the head of the SS ' s archaeological department , " Amt für Ahnenerbe " ( " Office for ancestral heritage " ) , and Himmler himself . Telling argued strongly against the destruction of an important remnant of " Aryan civilization " and Himmler authorized him to stop the construction of the anti - tank trench . He informed Telling that a written order would be dispatched but that it would take several days to arrive . Telling then drove to the site and ordered the commanding Wehrmacht officers to immediately stop the construction process . When the local Wehrmacht commander refused , Telling threatened him with reprisals from the SS . Construction was called off and Himmler ' s written order arrived two days later countering the Wehrmacht ' s original instructions . Telling later settled near the site and considered himself a custodian of it until his death in 1968 . The Danevirke in popular culture . As a symbol of Danish autonomy from Germany , " Dannevirke " was adopted as the title of several Danish journals during the nineteenth century . The most notable of these was published by N . F . S . Grundtvig from 1816 – 19 . The town of Dannevirke in New Zealand was founded by Danish , Norwegian and Swedish settlers in 1872 , when the Danevirke ' s loss to the Germans was a recent and very painful memory . " Parts of this article are based on the articles and on the Danish Wikipedia , accessed on 23 July 2006 . "