Sotah 43 - Exclusions from military service
After the Kohen at war has spoken the words we discussed , it is the turn of army leaders to list exceptions. Anyone who built a new house but has not lived there - he should go back. This applies to buying the house, not only to building it, and the type of house can as well be a barn, woodshed, or any other livable structure.
Anyone who planted a vineyard and has not used it (this includes three years of it being "orlah" and the fourth year after that) - goes back. And anyone who has engaged a woman but did not get married to her - he goes back to his wife and spends a year with her. Finally, anyone who is scared also goes back. He may feel that he did something wrong and therefore he does not have the merit to win in war. Other reasons are mentioned first so that people who are afraid do not have to be humiliated by admitting it.
However, these exceptions apply only to voluntary wars that Sanhedrin approves for national reasons. If enemies wage a war against Israel with the intent to harm, it is a mitzvah for everyone to participate.
Art: The Engagement Ring by John Shirley Fox