The human instrument for the establishment of the Work was Mrs. Gabriele Bitterlich, known in the OA affectionately as "Mother Gabriele", or simply "Mother". She was born Gabriele Göhlert on November 1, 1896 in Vienna. In 1919 she married Dr. Hans Bitterlich; God blessed them with three children, and they adopted an additional three after World War II. For many years, Mother Gabriele was under the direction of different religious priests from the diocese of Innsbruck. Some time after the death of her husband, she took up residence at the Motherhouse of the Order, the castle St. Petersberg, in Silz, Tirol, where she died on April 4, 1978.
Over the years, through the inspirations given to Mrs. Bitterlich, the faithful became increasingly aware already during her lifetime of the presence of the holy angels and, in union with the mystery of Christ's Cross, their salvific mission in the Church. Consequently, people from all states of life joined the growing Opus Angelorum movement, which resulted in the erection of various ecclesial associations with approbation from local Bishops. In 1961, the first association of the faithful in the Work of the Holy Angels, the Confraternity of the Holy Guardian Angels, was erected by Bishop Rusch in Innsbruck. Since then, an old medieval Order, the Order of Canons Regular of the Holy Cross, was also restored by members of the OA with the final approbation of the Holy See in 1979.
The Society of Sisters of the Holy Cross, whose original rule was first approved in 1967, was erected as a pious union of the faithful in 1970 with private vows, and consequently as a religious institute of diocesan right with public vows in 2002. Other erections within the OA family include the Confraternity of Priests, the Brothers of the Cross (a third order), the Work Helpers (a pious union), and the OA Association of Families. The principal goals of the whole OA movement include the commitment to the spiritual support of the priesthood, to the sanctification of the faithful, and to the fostering of active collaboration with the holy angels for the needs of the Church and the salvation of souls.
Since the movement originated in a private charism, some German bishops were concerned and asked the Holy See to examine the writings of Opus Angelorum. For every spirituality of an ecclesial movement of the faithful in the Church must be firmly based on Sacred Scripture and Tradition, and not merely on private revelations. The writings of Gabriele Bitterlich were therefore studied by the Congregation for the Doctrine of Faith from 1977 to 1983, which resulted in regulatory decrees of 1983 and 1992, limiting the use of Mother Gabriele's writings and (the latter) discontinuing the practice of consecrations to the holy angels until further clarifications were made.
At that time, a delegate of the Holy See, Fr. Benoît Duroux, was appointed to oversee the implementation of the decrees, and the integration and development of the Opus Angelorum, also in its relationship to the Order of the Holy Cross and the Sisters of the Holy Cross. This supervision was most beneficial for the growth of the OA and the respective communities. The overall direction of the Opus Angelorum was entrusted to the Holy Cross Order and, in cooperation with the delegate, a theological commission was set up within the Order to present to the Congregation for the Faith the theological justification for the consecrations to the holy angels. In the Holy Year 2000, the same Congregation approved with the consent of Pope John Paul II the consecration to all the holy angels of the Opus Angelorum. At that point, essential elements of the spirituality of the OA were incorporated into the Constitutions (the Rule) of the Order of Canons Regular of the Holy Cross, which were then definitively approved by the Congregation for Religious in 2003.
On November 7, 2008, the revised Statutes for the Opus Sanctorum Angelorum, which also clarified the relationship of the OA to the Holy Cross Order, were then approved by the Holy See. It is now a public association of the faithful and a juridical person according to can. 313 of the Code of Canon Law, and is directed ex officio by the Prior General of the Order of the Holy Cross.