John M. Crisp introduces an excellent column on "Solving the puzzle of children, war" (17 April 2017) with the Christian trope contrasting the "god of wrath and battles" of much of the "Old Testament" with the kinder, gentler God of the New.
It's not that simple. The peace-and-love Jesus of the Beatitudes goes on to say, figuratively, "[…] I have not come to bring peace but a sword" (Matthew 5.2-12, 10.34). And both figuratively and Prophetically, John of Patmos presents a kick-ass Christ in his Apocalypse, "clad in a robe dipped in blood," with a "sharp sword with which to smite the nations" and "tread the wine press of the fury of the wrath of God," crushing the unsaved like grapes (Revelation 19.13-16). Later in the Book of Revelation, we get beautiful visions of "a new heaven and a new earth," for the saved. "But as for the cowardly, the faithless, the polluted, as for murderers, fornicators, sorcerers, idolaters, and all liars" — and later members of the wrong church, or those God just chose to damn — "their lot shall be in the lake that burns" forever (20.1, 4; 21.8).
In history, in A.D. 1099, the takingof Jerusalem to climax the First Crusade included a massacre near Temple Mount where Christian sources concede or brag, "[…] the slaughter was so great that our men waded in blood up to their ankles [...]" — or bridles and knees. "None of them" — Muslims in the area — "were left alive; neither women nor children were spared." The Jews of Jerusalem were burned.
Deusvult; God willed it.
So there's Jesus's " mercy and peace" that Crisp says, "we've never really tried"; and that lack of trying goes far back. Since antiquity, many have accepted Jesus only once that wimpy preaching gets toughened up.