Hemming was a Danish king for only two years, but his reign helped shape the future of Franco-Danish relations immeasurably. He was best known for signing the Treaty of Heiligen with the Frankish emperor Charlemagne in 811. The two men agreed to terms of peace during a harsh winter that prevented their delegations from meeting face to face. It wasn’t until the spring thaw that 12 Danish and 12 Frankish nobles met on the Eider River to confirm the peace by an exchange of oaths. The treaty created the southern boundary of Denmark at the Eider River.