A minor at the time of his father's death in 1336, Bolesław III inherited his domains under the regency of his paternal uncles Siemowit II and Trojden I until 1340, when he attained his majority and began his personal government.
Probably since the beginning of his reign, Bolesław III paid homage to King John of Bohemia, who guaranteed the integrity of his domains, located between two powerful neighbors, the Teutonic Order and Poland.
At some point, even Bolesław III agreed to name the Polish King his heir in default of male offspring, which clearly was against the policy of the Luxembourg dynasty, rulers of Bohemia.
The campaign was a complete success, especially since on 15 August 1351 was concluded with the Lithuanians a truce under which Kęstutis accept Christianity and to this end, he was placed under the care of the Duke of Płock as an honorable prisoner.
However, soon became notorious that Kęstutis had no intentions to comply with the agreement, because five days later (20 August), he decided to escape in his route to Buda after attacked Boleslaw III by surprise with his troops.