He is well known for his intellectualism, the development of social teachings with his famous papal encyclical Rerum Novarum and his attempts to define the position of the Catholic Church with regard to modern thinking. He influenced Roman Catholic Mariology and promoted both the rosary and the scapular. He issued a record eleven encyclicals on the Rosary earning the moniker the "Rosary Pope", approved two new Marian Scapulars and was the first pope to fully embrace the concept of Mary as Mediatrix. He was the first pope to never have held any control over the Papal States, after they were dissolved by 1870.

The title "Mediatrix" is used in Roman Catholic Mariology to refer to the intercessory role of the Virgin Mary as a mediator in the salvific redemption by her son Jesus Christ, and that he bestows graces through her. Mediatrix is an ancient title that has been used by a number of saints since at least the 5th century. Its use grew during the Middle Ages and reached its height in the writings of saints Louis de Montfort and Alphonsus Liguori in the 18th century.^[2] A general role of mediation or intercession is attributed to Mary in Roman Catholicism, Eastern Orthodoxy and Oriental Orthodoxy,^[3] and the term "Mediatrix" was applied to her in the dogmatic constitution Lumen gentium of the Second Vatican Council. "This, however, is to be so understood that it neither takes away from nor adds anything to the dignity and efficaciousness of Christ the one Mediator."^[4]The use of the title Mediatrix and the doctrine of Mary having a higher level of saintly intercession (owing to her special relationship with her son Jesus) is distinct from the theological issues involved in the establishment of Mediatrix of all graces as a dogma, which is still being debated among Catholic theologians, but has not received Vatican approval

Let us think about this for a minute. This happened in 1884. The devil said he needed 75 to 100 years. Well, 75 years from 1884 is 1959. Wow, what a coincidence that it was on January 25, 1959, that John XXIII publicly summoned the Second Vatican Council. Remember that after the vision, Pope Leo XIII immediately wrote the Prayer to St. Michael to help us overcome the devil in his quest. He instructed that it be said after every low Mass. One of the first changes to come from Vatican II, was the deletion of the Leonine Prayers which included the prayer to St. Michael.
These prayers were eliminated in 1964, the 80th year of the devils 75 - 100 years needed to destroy the Catholic Church. It would seem that this would be the time to especially say that prayer, not to delete it.

The 100th year would be 1984. By 1984 church developed, that is called Catholic, but is not. The devil has twisted and distorted church teachings so much that there truly is a brand new church, a new order (Novus Ordo) and the true church has been reduced in population to a mere shell of what it once was, but it will survive: "That thou art Peter; and upon this rock I will build my church, and the gates of hell shall not prevail against it. And behold I am with you all days, even to the consummation of the world." Matt. 16:18 & 28:20

Here is the original version of the prayer to St. Michael, written by Pope Leo XIII in 1884. The shorter version follows, which is the version said after low Masses.

Prayer to Saint Michael the Archangel

-- Most glorious Prince of the Heavenly Armies, Saint Michael the Archangel, defend us in "our battle against principalities and powers, against the rulers of this world of darkness, against the spirits of wickedness in high places"(Ephes., VI, 12). Come to the assistance of men whom God has created to His likeness and whom He has redeemed at a great price from the tyranny of the devil. Holy Church venerates thee as her guardian and protector; to thee, the Lord has entrusted the souls of the redeemed to be led into heaven.
Pray therefore the God of Peace to crush Satan beneath our feet, that he may no longer retain men captive and do injury to the Church. Offer our prayers to the Most High, that without delay they may draw His mercy down upon us; take hold of the dragon, "the old serpent, which is the devil and Satan," bind him and cast him into the bottomless pit "so that he may no longer seduce the nations"(Apoc. XX.2). In the Name of Jesus Christ, our God and Lord, strengthened by the intercession of the Immaculate Virgin Mary, Mother of God, of Blessed Michael the Archangel, of the Blessed Apostles Peter and Paul and all the Saints, we confidently undertake to repulse the attacks and deceits of the devil. "Let God arise, let His enemies be scattered; let those who hate Him flee before Him. As smoke is driven away, so drive them away; as wax melts before the fire, so the wicked perish at the presence of God. ” (Ps. 67) V.
Behold the Cross of the Lord, flee bands of enemies. R. He has conquered, the Lion of the tribe of Juda, the offspring of David. V. May Thy mercy, Lord, descend upon us. R. As great as our hope in Thee.

(at the "+" make the sign of the Cross)

We drive you from us, whoever you may be, every unclean spirit, all satanic powers, all infernal invaders, all wicked legions, assemblies and sects; in the Name and by the power of Our Lord Jesus Christ, + may you be snatched away and driven from the Church of God and from the souls made to the image and likeness of God and redeemed by the Precious Blood of the Divine Lamb. + Most cunning serpent, you shall no more dare to deceive the human race, persecute the Church, torment God's elect and sift them as wheat. + The Most High God commands you. + He with whom, in your great insolence, you still claim to be equal, "He who wants all men to be saved and to come to the knowledge of the truth"(1 Tim., 11.4).
God the Father commands you. + God the Son commands you. + God the Holy Ghost commands you. + Christ, God's Word made flesh, commands you. + He who to save our race outdone through your envy, humbled Himself, becoming obedient even unto death"(Phil, 11,8); He who has built His Church on the firm rock and declared that the gates of hell shall not prevail against Her, because He will dwell with Her "all days even to the end of the world" (St. Mat., XXVIII,20).
The sacred Sign of the Cross commands you, + as does also the power of the mysteries of the Christian Faith. + The glorious Mother of God, the Virgin Mary, commands you. + She who by her humility and from the first moment of her immaculate Conception, crushed your proud head. The faith of the Holy Apostles Peter and Paul and of the other Apostles commands you. + The blood of the Martyrs and the pious intercession of all the Saints command you. + Thus, cursed dragon, and you, diabolical legions, we adjure you by the living God, + by the true God, + by the holy God, + by the God "who so loved the world that He gave up His only Son, that every soul believing in Him might not perish but have life everlasting" (St. John, III); stop deceiving human creatures and pouring out to them the poison of eternal damnation; stop harming the Church and hindering her liberty. Begone, Satan, inventor and master of all deceit, enemy of man's salvation. Give place to Christ in whom you have found none of your works; give place to the One, Holy, Catholic and Apostolic Church acquired by Christ at the price of His Blood. Stoop beneath the all-powerful Hand of God; tremble and flee when we invoke the Holy and terrible Name of Jesus, this Name which causes hell to tremble, this Name to which the Virtues, Powers and Dominations of Heaven are humbly submissive, this Name which the Cherubim and Seraphim praise unceasingly repeating: Holy, Holy, Holy is the Lord, the God of Armies. V. O Lord, hear my prayer. R. And let my cry come unto Thee. V. May the Lord be with thee. R. And with thy spirit. Let us pray. God of Heaven, God of earth, God of Angels, God of Archangels, God of Patriarchs, God of Prophets, God of Apostles, God of Martyrs, God of Confessors, God of Virgins, God who has power to give life after death and rest after work, because there is no other God than Thee and there can be no other, for Thou art the Creator of all things, visible and invisible, of whose reign there shall be no end, we humbly prostrate ourselves before Thy glorious Majesty and we beseech Thee to deliver us by Thy power from all the tyranny of the infernal spirits, from their snares, their lies and their furious wickedness; deign, O Lord, to grant us Thy powerful protection and to keep us safe and sound.
We beseech Thee through Jesus Christ Our Lord. Amen.

From the snares of the devil, deliver us, O Lord. That Thy Church may serve Thee in peace and liberty, we beseech Thee to hear us. That Thou may crush down all enemies of Thy Church, we beseech Thee to hear us. (Holy water is sprinkled in the place where we may be.) The Shorter Version (Said after Low Mass) 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 power of God, thrust into Hell, Satan and all the other evil spirits, who prowl throughout the world, seeking the ruin of souls. Amen