As a youngest son he was destined for a church career and became a
deacon in Osnabrück. After the death of Bishop
Dietrich in 1403, Henry was appointed as his successor. But then, both of his older brothers died young:
Albert II fell off his horse in a battle against
Dithmarschen in 1403 and
Gerhard VI fell in the Battle on the Hamme. This left Henry III as his father's only surviving son, so he declared himself the heir, not only of Holstein-Rendsburg, but also of the
Duchy of Schleswig, which had been given as a hereditary
fief to Gerhard VI in 1386. Queen
Margaret I of Denmark and her successor, King
Eric I of Denmark objected. They saw this as an opportunity to bind Schleswig more strongly to Denmark. Eric I invited Henry III and other nobility to
Kolding. Henry was then lured to Hindsgavl on
Fyn island, where he was arrested. For his release, he had to pay and he had to pledge
Flensburg to Denmark for a year. Eric accepted the transfer of Flensburg, but not Henry's money. This led to a war between Holstein-Rendsburg and Denmark. On 13 July 1409, Eric made an alliance with Ditmarsh. On 12 August 1410, armies from Holstein-Rendsburg and Denmark fought a battle in moorland near
Sollerup in the district of Eggebek. Holstein-Rendsburg won, and the Danish army leader Mogens Munk fell in battle. On 26 March 1411, a compromise was negotiated in Kolding. Margaret I died in October 1412 and the nobility from Holstein refused to return the territories they'd occupied in 1410, as had been agreed in the compromise of 1411. Eric I took the case to a feudal court in
Nyborg, which ruled on 29 July 1413 that Henry III had forfeited his duchy. Danish troops then occupied Schleswig. Henry made an alliance with the city of
Hamburg, which did not want a powerful neighbour. In 1419, Danish troops conquered
Fehmarn and looted it. Holstein-Rendsburg counterattacked and was victorious in the battle of Immerwad, near
Haderslev. A new truce was agreed on 26 November 1420. In early 1421, Henry III was elected Bishop of Schleswig. However, he died in February, before he could assume office. == References ==