By felicitous coincidence, the calendar of the Missal of Paul VI celebrates the Feast of Christ the King (AKA, Christ King of the Universe) on the same day, its being the last Sunday of the Church calendar. In the older calender, the feast of Christ the King is celebrated earlier (October 26th in 2014.)
Pius Xi proclaimed the feast in 1925. Fr. José Ramón Miguel Agustín Pro Juárez, S.J., was martyred November 23, 1927 proclaiming with his arms in the form of a cross "Viva Cristo Rey!" John Paul II proclaimed him beatified on September 25, 1988 in Mexico.
This was during the uprising of the Cristeros and if you have not seen the movie, do!
As to the reign of Christ, Pope Francis puts it this way: "Jesus is not a King according to earthly ways: for him, to reign is not to command, but to obey the Father, to give himself over to the Father, so that his plan of love and salvation may be brought to fulfillment. In this way there is full reciprocity between the Father and the Son. The period of Christ’s reign is the long period of subjecting everything to the Son and consigning everything to the Father."