In the 20th century, two great organizations were founded in Western and Eastern Europe respectively to spread the Kingdom of Christ through Marian consecration.
On Oct. 16, 1917, St. Maximilian Kolbe (1894-1941) founded the Militia Immaculatae (MI), a movement to counter the bad influence of Freemasons and Modernists. MI members consecrated themselves to Our Lady and became her knights to introduce and to foster Marian devotion among strayed and indifferent souls, thus helping extend as far as possible the blessed kingdom of the most Sacred Heart of Jesus. The sign of Marian consecration of MI members is the Miraculous Medal.
In 1941, Maximilian Kolbe was captured by the Nazis. As a prisoner in Auschwitz, Maximilian frequently led the other prisoners in praying the rosary, especially those who shared his cell. In August 1941, Maximilian gave his life by voluntarily replacing a younger man in the starvation bunker.
The Militia Immaculatae promoted Marian consecration in Poland and the Legion of Mary promoted it in Ireland. Both organizations would eventually spread throughout the world.
The Legion of Mary was founded by Frank Duff (1889-1980). Duff came from a wealthy family in Dublin, Ireland. At the age of 24, he became aware of the extreme poverty of many people in Ireland and began to help them through serving at the Society of St. Vincent de Paul. Charitable works led Duff to desiring a more devout way of life. As a result, in 1914 he started to attend two Masses each day and continued this practice for the rest of his life.
In 1917, the same year that Our Lady appeared in Fatima and St. Maximilian founded the Militia Immaculatae, Duff read St. Louis de Montfort's True Devotion to the Blessed Virgin. This book helped deepen his devotion to Our Lady. He began to teach everyone that if they did not understand Mary, they were incapable of understanding Christianity.
On Sept. 7, 1921, Frank Duff founded the Legion of Mary, which followed the spirituality of St. Louis de Montfort in its Marian devotion and piety. The Legion of Mary is an army of the Mother of God, bringing souls to Jesus through Mary.
Like the Militia Immaculatae, consecration to Our Lady is an important highlight of the Legion of Mary spirituality. Each year, around March 25, the Solemnity of the Annunciation, members of the Legion of Mary assemble together and renew their own consecration to Mary, saying, "I am all yours, my Queen, my Mother, and all that I have is yours."
The Legion of Mary became an extremely fruitful Marian apostolate during the 20th century. The Legion was represented in almost every diocese in the world, and Blessed Pope Paul VI described it as the greatest movement to help souls since the establishment of the mendicant religious orders.
Frank Duff emphasized that the rosary is the core of the Legion of Mary spirituality. He mandated each group of Legion of Mary to pray the rosary as part of their weekly meeting. He also encouraged each member to join the Confraternity of the Rosary.
Duff said that the rosary is the "Prime devotion to the Holy Spirit," for the contents of the rosary – the mysteries – celebrate the principal interventions of the Holy Spirit in the drama of redemption.
Duff wanted the rosary to be prayed with dignity and respect, insisting that those praying the second half of the Hail Mary were not to start before the person praying the first half had said the Holy Name of Jesus.
In 1965, Pope Paul VI invited Duff to attend the Second Vatican Council as a lay observer. He died at age 91 on Nov. 7, 1980.