He married a relative of King Valdemar I of Denmark and had two brothers, Helmold and Volrad; the latter was not, as often supposed, the first Count of Dannenberg.
In response to a raid by the Obotrite prince Pribislav, Henry led a campaign into Wagria against the Polabian Slavs.
The lands around Plön, Lütjenburg, and Oldenburg were laid waste, as was the region between the Schwale, the Baltic Sea, and the Trave.
The newly created County of Ratzenburg included Ratzeburg, Boitin, Gadebusch, Wittenburg, and Boizenburg.
The count pursued a policy of expelling the native Slavs and inviting Westphalians to settle in the conquered territory.