God for whom we wait,
Lord of night and the solemn beauty of darkness:
you have grieved over your creation,
over our swords and all the terrible weapons, we fashion.
Nations and peoples live in fear: how can we make tools of our swords
or take the wages of our weapons to feed the hungry?
Give us, Lord, a love that is greater than our fear.
We wait for the Messiah,
keeping watch and praying in his name,
Jesus, who is Lord forever and ever. Amen.

Catholic Household Blessings and Prayers, 1988

The coming of God’s Son to earth is an event of such immensity that God willed to prepare for it over centuries. He makes everything converge on Christ: all the rituals and sacrifices, figures and symbols of the “First Covenant”. He announces him through the mouths of the prophets who succeeded one another in Israel. Moreover, he awakens in the hearts of the pagans a dim expectation of this coming.

St. John the Baptist is the Lord’s immediate precursor or forerunner, sent to prepare his way. “Prophet of the Most High”, John surpasses all the prophets, of whom he is the last.  He inaugurates the Gospel, already from his mother’s womb welcomes the coming of Christ, and rejoices in being “the friend of the bridegroom”, whom he points out as “the Lamb of God, who takes away the sin of the world”. Going before Jesus “in the spirit and power of Elijah”, John bears witness to Christ in his preaching, by his Baptism of conversion, and through his martyrdom.

When the Church celebrates the liturgy of Advent each year, she makes present this ancient expectancy of the Messiah, for by sharing in the long preparation for the Savior’s first coming, the faithful renew their ardent desire for his second coming. By celebrating the precursor’s birth and martyrdom, the Church unites herself to his desire: “He must increase, but I must decrease.”

Catechism of the Catholic Church 522-524

We preach not one advent only of Christ, but a second also, far more glorious than the former. For the former gave a view of His patience; but the latter brings with it the crown of a divine kingdom….In His former advent, He was wrapped in swaddling clothes in the manger; in His second, He covers Himself with light as with a garment. In His first coming, He endured the Cross, despising shame Hebrews 12:2; in His second, He comes attended by a host of Angels, receiving glory.

…Our Lord Jesus Christ, then, comes from heaven; and He comes with glory at the end of this world, in the last day. For of this world there is to be an end, and this created world is to be re-made anew.

Cyril of Jerusalem, Catechetical Lecture 15;
http://www.newadvent.org/fathers/310115.htm