Pope Leo XIII wrote the Saint Michael prayer in 1884, after supposedly seeing a frightening vision: evil spirits, trying to fulfill Satan’s boast to destroy our Lord’s Church within a century, were engaging in fierce attacks against it.

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.