The Brandenburg Ascanians were suzerains of the Duchy of Pomerania and in return for military and financial help he gave oath of fealty and paid homage over a couple Pomeralian to these dukes.

Surrounded by adversity and even taken prisoner (for a short time in 1270) Mestwin II gave the possession of Danzig to the Brandenburg duke Conrad who was holding the city of Danzig until Mestwin II forced them to resign from their possession of the city by use of force in 1273, having been strengthened by new alliance with his maternal cousin Bolesław Pobożny, the duke of Great Poland.

Defeated Wartislaw II found refuge with Ziemomysł of Kuyavia, the duke of Inowrocław and sought assistance from the Order, but he died unexpectedly in Wyszogród in 1271.

It seems that the treaty of Kępno in fact unified Pomerelia and Greater Poland, starting the long process of reunification of Polish principalities by the Piast dynasts.

During the life of Mestwin II nobles and magnates of Greater Poland received grants and appointments to Pomerelian offices and estates.

These treaties resulted directly from aggressive policies of March of Brandenburg and the Teutonic Order against the territories of these Slavic duchies and provinces.