Hemming was the Danish king who made peace with Charlemagne in the 811 Treaty of Heiligen. He succeeded Gudfred and pursued a settlement with the Frankish emperor after years of frontier conflict.
Gudfred’s campaigns against the Obotrites and his 810 raid on Frisia had brought Denmark and the Frankish Empire close to war. After Gudfred’s assassination, Hemming offered peace. The agreement was confirmed at Heiligen, a place near the Eider River, by delegations representing both sides.
The treaty involved an exchange of gifts and oaths. Twelve Danish magnates and twelve Frankish representatives participated, and the settlement is recorded in the Royal Frankish Annals under 811. Severe winter conditions delayed the formal oath exchange until roads became passable in spring.
The treaty is often described as establishing the Eider as Denmark’s southern boundary, but that interpretation should be treated cautiously: the contemporary evidence more clearly records a peace agreement and frontier settlement than a fully defined modern border. Hemming died the following year, after which a Danish succession struggle broke out.