So, too, the evil which today torments humanity can be conquered only by a world-wide crusade of prayer and penance. We ask especially the Contemplative Orders, men and women, to redouble their prayers and sacrifices to obtain from heaven efficacious aid for the Church in the present struggle. Let them implore also the powerful intercession of the Immaculate Virgin who, having crushed the head of the serpent of old, remains the sure protectress and invincible "Help of Christians." (Papal Encyclical, Divini Redemptoris, 19 March 1937).