The Counter-Reformation was the Catholic Church's roughly century-long response to the Protestant Reformation, running from the opening of the Council of Trent in 1545 to the Peace of Westphalia in 1648. It combined an internal reform of the clergy and doctrine with a combative campaign to define Catholic belief against Protestantism and to win back lost ground.
The same movement that dragged Galileo before a tribunal also carved Bernini's swooning saint and sent Jesuits to the far side of the world. To later observers it looked like a Church at war with the modern mind. To Catholics it was the moment their faith saved itself. Even the name is a fight: was this a reaction to Luther, or a renewal that had begun before anyone had heard of him?