Early in his reign, he conducted an unsuccessful war against Nicholas II of Werle about the succession of Henry I.

Lord Nicholas I of Rostock put his country in 1300 under the feudal rule and protection of King Eric VI of Denmark.

The trigger for this war was the refusal of Wismar to host the wedding of Henry's daughter Matilda with Duke Otto III of Brunswick-Lüneburg.

The city rose up again in 1313, when Henry was undertaking a pilgrimage to the Madonna del Rocca church in Castelmola.

He defeated Waldemar in the Battle of Gransee and was finally awarded the Lordship of Stargard in the Treaty of Templin of 25 November 1317.

In 1323, Rostock revolted again, and Henry subdued the city again and made peace with King Christopher II of Denmark on 21 May 1323.

The new Margrave Louis I of Brandenburg, or rather his guardian Count Berthold VII of Henneberg-Schleusingen, reconquered Prignitz and the Uckermark and Henry had to settle for an unfavourable peace treaty on 24 May 1325.

It ended after fierce fighting with the Peace of Brudersdorf of 27 June 1328, in which Pomerania acquired Rügen and Mecklenburg had to settle for a monetary compensation.