I answer that, As stated above (A. 3), it belongs to the virtue of fortitude to guard the will against being withdrawn from the good of reason through fear of bodily evil. Now it behooves one to hold firmly the good of reason against every evil whatsoever, since no bodily good is equivalent to the good of the reason. Hence fortitude of soul must be that which binds the will firmly to the good of reason in face of the greatest evils: because he that stands firm against great things, will in consequence stand firm against less things, but not conversely. Moreover it belongs to the notion of virtue that it should regard something extreme: and the most fearful of all bodily evils is death, since it does away all bodily goods. Wherefore Augustine says (De Morib. Eccl. xxii) that "the soul is shaken by its fellow body, with fear of toil and pain, lest the body be stricken and harassed with fear of death lest it be done away and destroyed." Therefore the virtue of fortitude is about the fear of dangers of death.
Reply Obj. 1: Fortitude behaves well in bearing all manner of adversity: yet a man is not reckoned brave simply through bearing any kind of adversity, but only through bearing well even the greatest evils; while through bearing others he is said to be brave in a restricted sense.
Reply Obj. 2: Since fear is born of love, any virtue that moderates the love of certain goods must in consequence moderate the fear of contrary evils: thus liberality, which moderates the love of money, as a consequence, moderates the fear of losing it, and the same is the case with temperance and other virtues. But to love one's own life is natural: and hence the necessity of a special virtue modifying the fear of death.
Reply Obj. 3: In virtues the extreme consists in exceeding right reason: wherefore to undergo the greatest dangers in accordance with reason is not contrary to virtue. _______________________
FIFTH ARTICLE [II-II, Q. 123, Art. 5]
Whether Fortitude Is Properly About Dangers of Death in Battle?
Objection 1: It seems that fortitude is not properly about dangers of death in battle. For martyrs above all are commended for their fortitude. But martyrs are not commended in connection with battle. Therefore fortitude is not properly about dangers of death in battle.
Obj. 2: Further, Ambrose says (De Offic. i) that "fortitude is applicable both to warlike and to civil matters": and Tully (De Offic. i), under the heading, "That it pertains to fortitude to excel in battle rather than in civil life," says: "Although not a few think that the business of war is of greater importance than the affairs of civil life, this opinion must be qualified: and if we wish to judge the matter truly, there are many things in civil life that are more important and more glorious than those connected with war." Now greater fortitude is about greater things. Therefore fortitude is not properly concerned with death in battle.
Obj. 3: Further, war is directed to the preservation of a country's temporal peace: for Augustine says (De Civ. Dei xix) that "wars are waged in order to insure peace." Now it does not seem that one ought to expose oneself to the danger of death for the temporal peace of one's country, since this same peace is the occasion of much license in morals. Therefore it seems that the virtue of fortitude is not about the danger of death in battle.
On the contrary, The Philosopher says (Ethic. iii) that fortitude is chiefly about death in battle.