The parallel here is not valid, annalex, because Christ could not die unless He willed Himself to die. But He did not commit the act of self-murder! And neither does your soldier. A soldier who dies in an act of heroism does not want to die even though he probably realizes he will.
Jesus' death, however, was necessary in order for it to be followed with a Resurrection, without which there would be no Chrisitanity. This is a tricky thing — for if we are to take it literally, people would be committing suicide all over the place! Christ died like any ordinary human being would die — from the wounds inflicted on Him, by His own permission.
Neither the acts of Christ or a soldier are positive (in the context of suicide) as they did not cause their own death by either self-crucifixion or by self-targeting in a war. Nore are they direct because neither Christ or the soldier desire to be dead as the primary goal. On negative indirect suicide (of an ordinary human) the Catholic Encyclopedia has this to say:
The soldier, engaged in an act of war likely to end up with his death, is not suicidal as long as he does attempt to survive, e.g. by taking cover when possible. In the case of Christ, since He intended to rise again and destroy death in general, but also His own death, the analogy holds inasmuch as He willed not only His death but also His resurrection. Naturally the distinction between ordinary and extraordinary means of survival, contemplated in the article, do not apply to Christ.D. Negative and Indirect Suicide
Negative and indirect suicide without the consent of God is also an attempt against the rights of the Creator and an injustice towards Him whenever without sufficient cause a man neglects all the means of preservation of which he should make use. If a man as usufructuary is obliged in justice to preserve his life, it follows that he is equally bound to make use of all the ordinary means which are indicated in the usual course of things, namely:
- he should employ all the ordinary means which nature itself provides, such as to eat, drink, sleep, and so on;
- moreover, he should avoid all dangers which he may easily avoid, e.g. to flee from a burning house, to escape from an infuriated animal when it may be done without difficulty.
In fact to neglect the ordinary means for preserving life is equivalent to killing one's self, but the same is not true with regard to extraordinary means. Thus theologians teach that one is not bound in order to preserve life to employ remedies which, considering one's condition, are regarded as extraordinary and involving extraordinary expenditure; one is not obliged to undergo a very painful surgical operation, nor a considerable amputation, nor to go into exile in order to seek a more beneficial climate, etc. To use a comparison, the lessee of a house is bound to take care of it as becomes a good father of a family, to make use of the ordinary means for the preservation of the property, for instance, to extinguish a fire which he may easily extinguish, etc., but he is not bound to employ means considered extraordinary, such as to procure the latest novelties invented by science to prevent or extinguish fire.