There are many titles of a Christian to describe one’s relationship to Christ. We are servants, disciples, friends, brothers and sisters, priests, prophets and kings, the Christian faithful, members of his mystical body by baptism and by the presence of the Holy spirit and sanctifying grace. For religious women, it is customary to call them “brides of Christ.” The Pope is often called the servant of the servants of Christ and, more popularly, the Vicar of Christ on earth. Priests and bishops are called shepherds, sharers in Christ, the head and bridegroom of the Church. Deacons are called servants of the Church in a special way. At the Second Vatican Council, the laity are challenged “to become apostles in the world to permeate the temporal order with the spirit of the gospel and so perfecting it” (Aposotolicam Actuositatem, 2).
One title that is not often discussed in theological literature or heard from the pulpit is the notion that was used to describe the identity of all Christians, lay and clerical, namely, “soldiers of Christ.” Perhaps this demise is due to the reality of killing in warfare as well as unjustly waged wars. However, a soldier is really someone interested in promoting peace in defense of the common good of his nation.
Notwithstanding, scattered throughout the New Testament is the notion that the follower of Christ battles against the world, flesh, and especially the devil, in order to keep his relationship with Christ by growing in virtue. Looking through the lens of Lumen Gentium, Gaudium et Spes and Aposotolicam Actuositatem, and the Compendium of the Social Doctrine of the Church, no one is ever called a soldier of Christ. “Battle” against evil is mentioned in passing only in Gaudium et Spes while the Catechism has several references to the battle for virtue (409, 410, 2275, 3725) but again does not use the appellation, “Soldier of Christ,” to describe the identity of a Christian.
On the other hand, St. Thomas Aquinas, following St. Paul’s many admonitions about the fight against sin and the temptations of the devil (too numerous to cite), has a great deal to say about this battle in his treatment of the Sacrament of Confirmation.
In his earlier work, Summa Contra Gentiles, IV, ch. 60, his teaching on Confirmation dealt with that issue when he begins his treatment:
 The perfection of spiritual strength consists properly in a man’s daring to confess the faith of Christ in the presence of anyone at all, and in a man’s being not withdrawn therefrom either by confusion or by terror, for strength drives out inordinate terror. Therefore, the sacrament by which spiritual strength is conferred on the one born again makes him in some sense a front-line fighter for the faith of Christ. And because fighters under a prince carry his insignia, they who receive the sacrament of confirmation are signed with the sign of Christ; this is the sign of the cross by which He fought and conquered. This sign they receive on the forehead as a sign that without a blush they publicly confess the faith of Christ.
Being a fighter under a prince is not an apt metaphor for our times, yet St. Paul tells us precisely to be fighters against the evil one or the devil and the flesh in numerous places of his writings.
St. Thomas continues with the notion of a fight against evil under the “prince” who is Christ:
 This signing takes place with a mixture of oil and balm which is called chrism, and not without reason. For by the oil one designates the power of the Holy Spirit, from whom Christ, too, is called “anointed” (Ps. 44:8; Luke 4:18); and consequently from Christ they are called “Christians” (Acts 9:26), so to say, as fighting under Him. And by the balm, through its fragrance, good repute is indicated. For the public confession of faith in Christ this good repute must be had by those who dwell among men of this world, brought forth, so to say, from the hidden recesses of the Church onto the field of battle.
Finally, Thomas uses the theme of “army” and “military forces” to help understand the significance of the Sacrament and it is related not so much to one’s personal sanctification, but in a relationship that is public or to others. He concludes speaking of those in the Church as being a spiritual military force, following St. Paul in 1 Timothy:
 Suitably, too, this sacrament is conferred only by bishops, who are in some sense the leaders of the Christian army. For even in secular military forces it is the prerogative of the army leader to select some men to be enrolled; so, also, those who receive this sacrament seem to be enrolled somehow in the spiritual military forces. Hence, also, a hand is laid upon them to designate the derivation of manliness from Christ.
Later in the in the Summa Theologiae, Thomas gives us a deepening of his doctrine. Now he will use the phrase “soldier” from I Tim. 2.3 as the metaphor (ST II-II 71, 3):
…in this sacrament the Holy Spirit is given for strength in the spiritual combat. Wherefore in this sacrament three things are necessary; and they are contained in the above form. The first of these is the cause conferring fulness of spiritual strength which cause is the Blessed Trinity: and this is expressed in the words, “In the name of the Father,” etc. The second is the spiritual strength itself bestowed on man unto salvation by the sacrament of visible matter; and this is referred to in the words, “I confirm thee with the chrism of salvation.” The third is the sign which is given to the combatant, as in a bodily combat: thus are soldiers marked with the sign of their leaders. And to this refer the words, “I sign thee with the sign of the cross,” in which sign, to wit, our King triumphed (cf. Col. 2:15).
And the combat is not only for one’s personal growth in virtue as he teaches in ad 3:
Baptism is the regeneration unto the spiritual life, whereby man lives in himself. And therefore in the baptismal form that action alone is expressed which refers to the man to be sanctified. But this sacrament is ordained not only to the sanctification of man in himself, but also to strengthen him in his outward combat.
St. Paul will also use the expression “wrestler” (Eph. 6.12) in this combat. Thomas further teaches (ST Ibid. 5 ad 2) that with Confirmation a person is given a power for kind of ministry:
Though he who is baptized is made a member of the Church, nevertheless he is not yet enrolled as a Christian soldier. All the sacraments are protestations of faith. Therefore just as he who is baptized receives the power of testifying to his faith by receiving the other sacraments; so he who is confirmed receives the power of publicly confessing his faith by words, as it were, “ex officio.”
Since the giving of the Holy Spirit at Pentecost is the final concluding act of Christ’s gift to the Church, Thomas claims it is given in its fullness when received as a sacrament (ST Ibid. 2):
Chrism is the fitting matter of this sacrament. For, in this sacrament the fullness of the Holy Ghost is given for the spiritual strength which belongs to the perfect age. Now when man comes to perfect age he begins at once to have interaction with others; whereas until then he lives an individual life, as it were, confined to himself.
Fullness of grace by the sacrament is given but one’s disposition, preparation for this plenitude among other circumstances may mean that only a small portion of that depth of grace is in fact received. I wonder if the evident collapse of the sexual morality of Catholics (high rate of divorce and remarriage, acceptance of contraception) has led to the denial of many doctrines of a higher nature that have diminished pastoral practice such as the massive decline in confession and Sunday Mass. Aquinas taught as much about the virtues, when he said, “Because whoever lacks them falls into the danger of false doctrine” (In 1 Tim, lecture two ).
If the Christian life, then, is not a battle but merely diluted belief, receiving Holy Communion now and again, then calling us soldiers is an anachronism. But looking where we are at present with the demise of priestly and religious vocations and bishops contradicting one another over Amoris laetitia, the Church could use some soldiering.