Pope Pius XI (pope from 1922 to 1939) did not hesitate to say: "Tell your priests that they must pray a lot. Until the Pope has said his rosary, the Pope's day does not end."
The same Pius XI wrote to Bishop Richaud: "The rosary is the most privileged means of procuring the return to Christ of individuals, families and nations. It is a very powerful weapon for driving out demons, for preserving the integrity of life, for acquiring virtue more easily, in a word, for obtaining true peace for men."
In 1938, in his Encyclical on the Rosary, Pius XI again said, regarding fidelity to the prayer of the Rosary: "How can we not hope for everything if we use this divine method with exactitude and piety?"
Source: www.serviteurs.org