When you go forth to battle against your enemies, and see horses, chariots, and people more numerous than you, you shall not fear them; for Hashem your God is with you, who brought you up from the land of Egypt. And when you approach the battle, the priest shall approach and speak to the people and say to them: "Hear, O Israel, this day you approach battle against your enemies. Let not your heart faint; fear not, nor be alarmed, or frightened by them, for it is Hashem your God who goes with you, to fight for you against your enemies, to save you." And the officers shall speak to the people, saying: 'What man is there that hath built a new house, and hath not dedicated it? let him go and return to his house, lest he die in the battle, and another man dedicate it...." (Devarim 20:1-5)
According to this passage, two things must be done before Israel fights a battle. The priest exhorts the people not to fear, and the officers tell several classes of people that they may return home without fighting.
Each of these things has its own logic, but what interests me now is the order in which they come. You would expect for the officers' dismissal to come before the priest's exhortation. After all, the best time to dismiss people from the army is when the army is being assembled, while the best time to give an inspiring speech is immediately before the battle. But as it is, the order is reversed. If you have a new wife, house, or vineyard, or if you are afraid, you must still join the army, and travel all the way to the battlefield, and hear the priest's speech before the battle, and only then can you go home. Wouldn't it be easier for such a person not to have to join the army in the first place?
I think that there is a lesson in this ordering, both for the soldiers in the Torah's battles, and for us today. There are people who have good reasons not to fight in battle. But this does not give them an excuse not to be part of the war. They must join the army, travel to the battlefield, experience the same tension everyone else experiences, and only then can they be sent home.
Similarly, certain Israelis today and all Jews abroad, who do not fight in the IDF, must nevertheless feel that they are part of the war, and look for tangible things they can do to help their relatives under fire. I am happy to report than, from what I have heard, in the recent Gaza war this is exactly what happened on a large scale.