O God, who to spread the greater glory of Thy name, didst, by means of blessed Ignatius, strengthen the church militant with a new army: grant that with his help and through his example we may so fight on earth as to become worthy to be crowned with him in heaven.

St. Ignatius Loyola was a man for others who marched under the Cross of Christ the King. The above prayer does not applaud some sort of militarism that counts "souls won for the Lord" like so many notches on a soldier's belt. Rather, the militaristic language of this prayer points to what is at stake: our very lives! A soldier is willing to die in the King's service: whosoever would save his life will lose it, but whosoever loses his life for my sake will find it.

Yet, the Gospel goes beyond and perfects such militarism. Our enemies are not non-believers. Rather, persons who have not heard or accepted the Gospel are the very ones we're working for, striving for, fighting for. Our weapons do not consist of bayonets or bullets, but the Sword of the Spirit, which is the Word of God (cf. Eph. 6). Our strengths lie not merely in our gifts, but in those places in ourselves where we are weak, that God's power may be made manifest in our weaknesses (cf. 2 Cor. 12:9).

This is a different militarism altogether. This is the militarism of the childlike heart that seeks only the triumph of the good and the defeat of the Evil One, the Enemy of our human nature (as St. Ignatius called him). This is the militarism of God: "The LORD is a warrior; LORD is His name!" (Ex. 15:3). GK Chesterton describes this childlike militarism:

A child's instinct is almost perfect in the matter of fighting; a child always stands for the good militarism as against the bad. The child's hero is always the man or boy who defends himself suddenly and splendidly against aggression. The child's hero is never the man or boy who attempts by his mere personal force to extend his mere personal influence. In all boys' books, in all boys' conversation, the hero is one person and the bully the other. 

But really to talk of this small human creature, who never picks up an umbrella without trying to use it as a sword, who will hardly read a book in which there is no fighting, who out of the Bible itself generally remembers the "bluggy" [bloody] parts, who never walks down the garden without imagining himself to be stuck all over with swords and daggers--to take this human creature and talk about the wickedness of teaching him to be military, seems rather a wild piece of humour. He has already not only the tradition of fighting, but a far manlier and more genial tradition of fighting than our own. No; I am not in favour of the child being taught militarism. I am in favour of the child teaching it.