Deuteronomy 20:7,8

Hath betrothed a wife The time allowed in this case was a year, Deuteronomy 24:5. This was a law of great humanity, that conjugal love might not be disturbed, but have time to knit into a firm and lasting affection. What man is fearful and faint-hearted This fearfulness is to be understood, say the Jews, not only of a natural timorousness, which is incident to some constitutions, and makes a man tremble at every danger, but of the adventitious terrors of a guilty conscience. For they did not, as in the modern fashion, send the wickedest and most worthless into the wars; but if they knew any man to be a notorious villain, they thrust him out of the army, lest his example should corrupt and discourage the rest of the soldiery.