The Council of Trent , held between 1545 and 1563 in Trento (Trent) and Bologna, northern Italy, was one of the Roman Catholic Church's most important ecumenical councils. Prompted by the Protestant Reformation, it has been described as the embodiment of the Counter-Reformation. Four hundred years later, when Pope John XXIII initiated preparations for the Second Vatican Council (Vatican II), he affirmed the decrees it had issued: "What was, still is."