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 Scanians 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 the Saxons of the Ottonian dynasty 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.