14 Notable among almost countless others was the unforgettable and savage onslaught on the Catholic religion which flared up in the 17th century in the Eastern countries. The Cossack forces then invaded those lands, and directed their furious attack on Catholics and their pastors, and on the heralds of the truth of the Gospel. Temples dedicated to the divine worship were utterly destroyed; monasteries were consumed by fire; priests and their flocks were everywhere put to the sword; everything was laid waste; all that was sacred was scattered to the winds.
Source: Invicti Athletae (Vatican.va)