Deuteronomy 20:1

Israel was at this time to be considered rather as a camp than as a kingdom, entering upon an enemy's country, and not yet settled in a country of their own; and, besides the war they were now entering upon in order to their settlement, even after their settlement they could neither protect nor enlarge their coast without hearing the alarms of war. It was therefore needful that they should have directions given them in their military affairs; and in these verses they are directed in managing, marshalling, and drawing up their own forces. And it is observable that the discipline of war here prescribed is so far from having any thing in it harsh or severe, as is usual in martial law, that the intent of the whole is, on the contrary, to encourage the soldiers, and to make their service easy to them. I. Those that were disposed to fight must be encouraged and animated against their fears. 1. Moses here gives a general encouragement, which the leaders and commanders in the war must take to themselves: "Be not afraid of them, Deu 20:1. Though the enemy have ever so much the advantage by their numbers (being more than thou), and by their cavalry (their armies being much made up of horses and chariots, which thou art not allowed to multiply), yet decline not coming to a battle with them, dread not the issue, nor doubt of success.

— Matthew Henry's Concise Commentary (public domain)