[2] When the minor Ladislaus IV of Hungary ascended the Hungarian throne in 1272, the kingdom fell into anarchy and many groupings of barons fought against each other for supreme power.

Peter's father Henry was one of the key figures in that period, who entered alliance with the Gutkeleds and the Geregyes, forming one of the two main baronial groups, while the other one was dominated by the Csák and Monoszló clans.

Henry was killed in the Battle of Föveny in late September 1274; thereafter his enemy Peter Csák gathered an army and marched into Western Hungary against the Kőszegis' domain in the autumn of 1274, but he couldn't break they power once and for all.

During the attack, 68 canons, priests and clergymen were killed, several others were tortured and robbed, while all the treasures of the Veszprém cathedral chapter, including the library and archives of its school were looted and burnt.

[9] In this capacity, Peter handed over his village Szentbékkálla to the cathedral chapter in exchange for the settlements Aracs (today a borough of Balatonfüred), Örményes and Udvari in April 1277.

In the upcoming years, the Pok brothers continued to plunder the Transdanubian estates of the bishopric, for instance they attacked and ravaged the church property in Tapolca, Csököly and Görgeteg around 1278, while also devastated the episcopal village Hegymagas in Zala County, slaughtering the local population.

[16][17] In retaliation, besides the punishment of excommunication, Peter Kőszegi's troops raided the family monastery of the Pok clan in the namesake village near Győr.

[18] Peter was present in October 1280 at Ozalj Castle along the river Kupa, when his brothers Nicholas, who was made Ban of Slavonia in that time, and Ivan concluded peace with their local enemies, the Babonići and Frankopans.

Nicholas, Henry, and – despite his clerical position – Bishop Peter stormed into Southern Transdanubia and jointly invaded and besieged the episcopal town of Pécs in March 1284.

[20] Around 1288, Rudolf of Hoheneck, the Archbishop of Salzburg promised Peter and Ivan that he was willing to offer assistance them against Duke Albert, and without their knowledge he will not reconcile with the members of the House of Habsburg.

[21] Peter Kőszegi and John Hont-Pázmány, Archbishop of Kalocsa stayed in Dióslápa (present-day Szentgáloskér) in Somogy County in August 1288, possibly as members of an ad hoc court.

[21] In response to Ivan's incursions, Duke Albert launched a massive royal campaign ("Güssing Feud"; German: Güssinger Fehde) with his 15,000-size army against the Kőszegis and their familiares' castles and forts in the spring of 1289.