And ye shall smite every fenced city, and every choice city, and shall fell every good tree, and stop all wells of water, and mar every good piece of land with stones. Shall fell every good tree - Every tree by which your enemies may serve themselves for fortifications, etc. But surely fruit trees are not intended here; for this was positively against the law of God, Deuteronomy 20:19, Deuteronomy 20:20 : "When thou shalt besiege a city - thou shalt not destroy the trees thereof - for the tree of the field is man's life - only the trees which thou knowest that they be not trees for meat, thou shalt destroy and cut them down."
Stop all wells of water - In those hot countries this would lead sooner than any thing else to reduce an enemy.
Mar every good piece of land with stones - Such a multitude of men, each throwing a stone on a good field as they passed, would completely destroy it.