But peace is the ‘tranquillity of order, divine, national, social, and individual, which ensures to everyone his place and gives him what is due to him, putting the glory of God above all duties and making the brotherly service of all derive from His love.’ And such is the human condition and the order of Divine Providence — without its having been possible hitherto to find a substitute for it — that war, though it is one of the most terrible scourges of mankind, yet sometimes it is the heroic and only remedy for replacing things on the centre of the pivot of justice and bringing them back to the Kingdom of Peace. Therefore the Church, even while she is the daughter of the Prince of Peace, blesses the emblems of war, has founded the military Orders, and has organized the Crusades against the enemies of the Faith.
Joint Letter of the Spanish Bishops to the Bishops of the Whole World Concerning the War in Spain, July 1st, 1937.
What a cruel thing is war; to separate and destroy families and friends, and mar the purest joys and happiness God has granted us in this world; to fill our hearts with hatred instead of love for our neighbours, and to devastate the fair face of this beautiful world! I pray that, on this day when only peace and good-will are preached to mankind, better thoughts may fill the hearts of our enemies and turn them to peace. … My heart bleeds at the death of every one of our gallant men.
— Gen. Robert E. Lee to his wife on Christmas Day, two weeks after the Battle of Fredericksburg (25 December 1862).