The Council of Trent, the 19th ecumenical council of the Roman Catholic church, was held at Trent in northern Italy between 1545 and 1563. It marked a major turning point in the efforts of the Catholic church to respond to the challenge of the Protestant Reformation and formed a key part of the Counter-Reformation. The need for such a council had long been perceived by certain church leaders, but initial attempts to organize it were opposed by Francis I of France, who feared it would strengthen Holy Roman Emperor Charles V, and by the popes themselves, who feared a revival of Conciliarism. The council eventually met during three separate periods (1545-47, 1551-52, 1562-63) under the leadership of three different popes (Paul III, Julius III, Pius IV). All of its decrees were formally confirmed by Pope Pius IV in 1564