Pope Leo XIII performed a number of consecrations, at times entering new theological territory.
After he had received many letters from Sister Mary of the Divine Heart, the countess of Droste zu Vischering and Mother Superior in the Convent of the Good Shepherd Sisters in Porto, Portugal, asking him to consecrate the entire world to the Sacred Heart of Jesus, he commissioned a group of theologians to examine the petition on the basis of revelation and sacred tradition.
The outcome of this investigation was positive and so in the encyclical letter Annum sacrum (on 25 May 1899), he decreed that the consecration of the entire human race to the Sacred Heart of Jesus should take place on 11 June 1899.

The encyclical letter also encouraged the entire Catholic episcopate to promote the First Friday Devotions, established June as the Month of the Sacred Heart, and included the Prayer of Consecration to the Sacred Heart.
His consecration of the entire world to the Sacred Heart of Jesus presented theological challenges in consecrating non-Christians.
Since about 1850, various congregations and countries had consecrated themselves to the Sacred Heart, and, in 1875, the consecration was made throughout the Catholic world.
Pope Leo XIII performed a number of consecrations, at times entering new theological territory. After he had received many letters from Sister Mary of the Divine Heart, the countess of Droste zu Vischering and Mother Superior in the Convent of the Good Shepherd Sisters in Porto, Portugal, asking him to consecrate the entire world to the Sacred Heart of Jesus, he commissioned a group of theologians to examine the petition on the basis of revelation and sacred tradition. The outcome of this investigation was positive and so in the encyclical letter Annum sacrum (on 25 May 1899), he decreed that the consecration of the entire human race to the Sacred Heart of Jesus should take place on 11 June 1899.
The encyclical letter also encouraged the entire Catholic episcopate to promote the First Friday Devotions, established June as the Month of the Sacred Heart, and included the Prayer of Consecration to the Sacred Heart. His consecration of the entire world to the Sacred Heart of Jesus presented theological challenges in consecrating non-Christians. Since about 1850, various congregations and countries had consecrated themselves to the Sacred Heart, and, in 1875, the consecration was made throughout the Catholic world.
Pope Leo XIII