In the early Middle Ages, the great Burgundian monastery of Cluny sponsored and encouraged an experiment in conciliation among its feudal neighbors — half-civilized landlords in a state of more or less endemic war with each other. The arrangement, known as "the truce of God," was that all hostilities should be restricted to three days in the week (Monday to Wednesday). Of course, this was never observed for any length of time with much consistency; and in retrospect its mixture of naive earnestness and cynicism is rather funny (very characteristic of the Church, somehow. . .). But it is more than a comical bit of medieval eccentricity. Behind it lay the recognition that for baptized Christians, sharers in the Body of Christ, to be in a state of war with one another was horrible and ridiculous. The mild ludicrousness of the response pales, however, in comparison with the absurdity of people, who could in principle kneel side by side to share the communion of Christ's body and blood, also planning revengeful slaughter against each other.
— Rowan Williams, The Truce of God