The actual title of count Dirk III was count in Friesland. West Friesland was very different from the area (North and South Holland) of today. Most of the territory was swamp, where nearly nobody lived. The main habitation was in the dunes at the coast and in the river valleys.
Dirk III was a member of the Gerulfingian dynasty (house of Holland), an important family within Germany at that time. His mother was regent in West Friesland from 993-1005 and was the sister in law of Henry II, Holy Roman Emperor.
Prior to 1018, Count Dirk III was a powerless vasal of Henry II but his fiefdom was in a strategically important location. Utrecht, situated in the Rhine delta, was the largest trading town of the German kings and traders had to sail through the territories of Dirk III, via the Rhine and Vecht rivers, in order to reach the North Sea.
Dirk III built his stronghold in Vlaardingen. He was not permitted to hinder trade in any way but eventually he defied imperial rule by levying toll. Merchants from the town of Tiel sent alarmed messages to the kings about acts of violence against them by Dirk III's men. The German emperor decided to end Dirk III's reign and awarded his lands to the bishop of Utrecht. A large imperial army then headed for Vlaardingen. The imperial army failed and the Battle of Vlaardingen was a tremendous victory for Dirk III.
Following his victory, Dirk III was permitted to keep his realm and he continued to levy toll.
After Dirk III's death in 1039, the imperial army returned on a few occasions seeking to reclaim the lands held by the Frisian counts. The powerful Robert I, Count of Flanders helped Dirk V, great-grandson of Dirk III and his own stepson, to restore Frisia to the counts.
It is thought that Dirk III went on pilgrimage to the Holy Land.
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The Annales Egmundani name "Theodricus III filius eius [=Arnulfi comitis]" when recording that he succeeded his father. The Chronologia Johannes de Beke names (in order) "Theodricum succedentem comitem…et Sifridum sive Sicconem presidem" as the children of Count Dirk III & his wife.
He succeeded his father in 993 as DIRK III Count of Holland. "Theodericus comes cum matre sua Lietgarda" donated "alodum suum situm secus fluvium Scaldum in pago Gandensi seu Tornacensi in vulla Rucga" to Saint-Pierre de Gand, for the soul of "patris sui Arnulfi", by charter dated 20 Sep 995. Count Dirk III had a stronghold in Vlaardingen, usurped property belonging to the bishop of Utrecht in the Vlaardingen area, and introduced a toll on ships passing along the river Merwede to Tiel without the consent of the emperor or the bishop. Thietmar records that "Dietrich the empress's nephew" attacked Adalbold Bishop of Utrecht in 1018, before his forces were attacked by the Frisians and suffered numerous casualties. "Thiederici Fresoniæ" witnessed a donation of property dated "Id Sep 1024" by "Hildigunda abbatissa de Gesike" and one dated "18 Kal Oct [1029]" by "Brun comes cum uxore sua Ida".
Beke's Egmondsch Necrologium records the death "1039 VI Kal Iun" of "tercius Theodericus Hollandie…comes". 1
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