The Solemnity of Christ the King, which every Catholic throughout the entire world is celebrating today, is a new thing. It was established by Pope Pius XI in 1925 in an encyclical letter called Quas primas.
The pope was writing this encyclical in 1925, when the world was still trying to recover from World War I, which had devastated Europe and shattered modernity's hopes for unlimited progress based solely on human reason.
1925 was also only a few years after the Russian Bolshevik Revolution, which had given birth to the world's first explicitly atheist totalitarian regime: Soviet communism. Everywhere the pope looked, he saw human societies abandoning Christian values and trying to build paradise on earth through other means.
But if humanity had been able to perfect itself by itself, without God's help, then Jesus Christ would never have come to earth.
Pope Pius XI instituted today's Solemnity as a way to remind the world that to reject Christ, either in private life or in public life, is to reject our only hope, and to accept him is to accept salvation.
As Pope Pius IX wrote: "...When once men recognize, both in private and in public life, that Christ is King, society will at last receive the great blessings of real liberty, well-ordered discipline, peace and harmony... That these blessings may be abundant and lasting in Christian society, it is necessary that the kingship of our Saviour should be as widely as possible recognized and understood, and to that end nothing would serve better than the institution of a special feast in honour of the Kingship of Christ." (Quas primas, 19, 21)
Fr. Paulus Waris Santoso, O.Carm