After the secularization of the Teutonic Order in 1525, a large part of its residents converted to Lutheran Protestantism.
Duke Albert, who had been grand master of the Order, sought to unite Warmia with Ducal Prussia (a nearby vassal state of Poland), causing the Catholics of the town to swear allegiance to the king of Poland in return for aid against Protestant Prussia.
In 1526 a Polish royal commission released Braunsberg burghers from the oath to the Polish king and handed the town back to Prince-Bishop Mauritius Ferber.
However, just like the entire area of Warmia, Braunsberg swore allegiance to the Prince-Bishops of Warmia, who were subjects of the popes.
 Additionally, it had to denounce all Lutheran teachings and hand over Lutheran writings.
Thereafter Warmia, though inhabited in part by ethnic Germans, remained predominantly Roman Catholic (even after the Partitions of Poland, when it became part of Prussia in 1772).

Braniewo was occupied by Sweden for about three years during the Livonian War in the 16th century.
In Warmia, Lutheran teachings again were suppressed when Prince-Bishop Stanislaus Hosius (1504-1579) brought in the Jesuits and founded the Collegium Hosianum school.
Among the students of the school were Polish Catholic Saint Andrew Bobola, Polish statesmen and high dignitaries Mikołaj Zebrzydowski and Piotr Gembicki, Europe's most prominent 17th-century Latin poet Maciej Kazimierz Sarbiewski, missionary, explorer, mathematician, astronomer and sinologist Jan Mikołaj Smogulecki, and Primate of Poland Gabriel Podoski.
Prominent Hungarian Renaissance poet Bálint Balassi stayed in the town in 1590–1591.
A priestly seminary was added in 1564.
Pope Gregory XIII later added a papal mission seminary for northern and eastern European countries.
Regina Protmann (1552-1613), a native of Braunsberg (Braniewo), founded the Saint Catherine Order of Sisters in the town, recognized by the church in 1583.
The Jesuit theologian Antonius Possevinus was instrumental in enlarging the Collegium Hosianum in the 1580s to counter the growing Protestant movement.

The Polish, and mainly Catholic town was annexed by the mostly Protestant Kingdom of Prussia in 1772 during the First Partition of Poland and made part of the province of East Prussia the following year.
After the secularization of the Teutonic Order in 1525, a large part of its residents converted to Lutheran Protestantism. Duke Albert, who had been grand master of the Order, sought to unite Warmia with Ducal Prussia (a nearby vassal state of Poland), causing the Catholics of the town to swear allegiance to the king of Poland in return for aid against Protestant Prussia. In 1526 a Polish royal commission released Braunsberg burghers from the oath to the Polish king and handed the town back to Prince-Bishop Mauritius Ferber. However, just like the entire area of Warmia, Braunsberg swore allegiance to the Prince-Bishops of Warmia, who were subjects of the popes.  Additionally, it had to denounce all Lutheran teachings and hand over Lutheran writings. Thereafter Warmia, though inhabited in part by ethnic Germans, remained predominantly Roman Catholic (even after the Partitions of Poland, when it became part of Prussia in 1772).
Braniewo was occupied by Sweden for about three years during the Livonian War in the 16th century. In Warmia, Lutheran teachings again were suppressed when Prince-Bishop Stanislaus Hosius (1504-1579) brought in the Jesuits and founded the Collegium Hosianum school. Among the students of the school were Polish Catholic Saint Andrew Bobola, Polish statesmen and high dignitaries Mikołaj Zebrzydowski and Piotr Gembicki, Europe's most prominent 17th-century Latin poet Maciej Kazimierz Sarbiewski, missionary, explorer, mathematician, astronomer and sinologist Jan Mikołaj Smogulecki, and Primate of Poland Gabriel Podoski. Prominent Hungarian Renaissance poet Bálint Balassi stayed in the town in 1590–1591. A priestly seminary was added in 1564. Pope Gregory XIII later added a papal mission seminary for northern and eastern European countries. Regina Protmann (1552-1613), a native of Braunsberg (Braniewo), founded the Saint Catherine Order of Sisters in the town, recognized by the church in 1583. The Jesuit theologian Antonius Possevinus was instrumental in enlarging the Collegium Hosianum in the 1580s to counter the growing Protestant movement.
The Polish, and mainly Catholic town was annexed by the mostly Protestant Kingdom of Prussia in 1772 during the First Partition of Poland and made part of the province of East Prussia the following year.
Braniewo