He spent the next few years in Germany, taking part in the Teutonic legation in Austria and collecting funds for the war with Świętopełk II, Duke of Pomerania-Gdańsk, who was supporting the Prussians in their first major revolt.

This, combined with severe Pomeranian losses inflicted upon by the Teutons and their growing coalition forced Swietopelk to sign a peace treaty with the Knights on 24 November 1248.

During the first expedition, shortly after taking power, members of his armies attempted to revolt, demanding that Heinrich be reinstated as master of Prussia, however, Poppo was able to appease the dissidents.

As the first Prussian revolt winded down, in 1247, he again left office and departed Prussia, spending the next six years of his life in Germany before being elected Grandmaster by the Teutonic Order in the wake of Gunther von Wullersleben's resignation.

Close co-operation with Holy Roman Emperor Fredrick II, who was in conflict with the Papacy, resulted in Pope Innocent IV threatening to excommunicate and disband the order.

In 1254, he dispatched an envoy, of which he was a part of, to King Ottokar II of Bohemia in order to obtain support for a crusade against the Sambians, who had inflicted upon the Teutons a devastating defeat earlier in the 1250s, killing Heinrich Stange, Komtur of Christburg.

Poppo proceeded to enslave the newly subjugated peoples to construct a stronghold in Konigsberg and several castles along the Vistula Lagoon.

On 24 July 1256 he helped secure a truce between Przemysł I, Duke of Greater Poland and Swietopelk II in Kcynia, having served as mediator during the negotiations.

Most likely, Poppo settled permanently in Prussia and lived there until the end of his life, with a short break in1264 and 1265, when he held the office of commander of Regensburg.