List_of_encyclicals_of_Pope_Leo_XIII_on_the_Rosary
During his pontificate, Pope Leo XIII wrote twelve encyclicals on the Rosary.
The first such encyclical was Supremi apostolatus officio of September 1883. Most were issued in September in anticipation of October, which Leo would have dedicated to Mary, in particular through the Rosary. The last one is Diuturni temporis. The first encyclicals established the rosary as a public devotion.[1]