Saint Michael the Archangel, defend us in battle. Be our protection against the wickedness and snares of the devil. May God rebuke him, we humbly pray; and do Thou, O Prince of the Heavenly Host – by the Divine Power of God – cast into hell, satan and all the evil spirits, who roam throughout the world seeking the ruin of souls.
Pope Leo XIII, realizing by Divine enlightenment the present and future struggles of the Church against the powers of hell, felt convinced that through the intervention of St. Michael, hell would be conquered, and the Church restored to peace and liberty.
He therefore composed a prayer in honour of the warrior archangel, and ordered it to be recited daily after Mass in all the churches throughout the Christian world.
This is how this prayer came to be written: It is said that one day having celebrated the Holy Sacrifice, the aged Pontiff Leo XIII was in conference with the Cardinals. Suddenly he sank to the floor in a deep swoon. Physicians who hastened to his side feared that he had already expired, for they could find no trace of his pulse. However, after a short interval the Holy Father rallied, and opening his eyes exclaimed with great emotion: "Oh what a horrible picture I was permitted to see!" He had been shown in spirit the tremendous activities of the evil spirits and their ravings against the Church. But in the midst of this vision of horror he had also beheld consoling visions of the glorious Archangel Michael, who had appeared and cast Satan and his legions back into the abyss of hell. Soon afterward he composed the well-known prayer.