It wasn’t quite a scorched-earth strategy, but it was close. The Israelites’ response was ruthless.
In revenge for their attempt to trick Israel into leaving God’s will, the Midianites lost their men and their kings in the battle, their villages were burned to the ground, their women and children were taken captive, and their cattle, flocks and other valuables were taken by the Israelites.
It was a normal part of war at the time (and for thousands of years afterwards): to the victor go the spoils (to use a more recent American saying). Israel’s military leaders were just following the normal conventions of war at the time.
But it wasn’t quite so easy in this case: the women were , as Moses pointed out:
Numbers 31:16 These are the very ones who followed Balaam’s advice and caused the people of Israel to rebel against the Lord at Mount Peor. They are the ones who caused the plague to strike the Lord’s people.
The command was, then, kill the women who could have been part of the deception—treat them as equal to the fighting men in a war that was no longer just military but also moral. Kill the boys (for obvious long-term military reasons), but spare the young girls.
The message must have gotten through to the Israelite military leaders:
Numbers 31:48-50 Then all the generals and captains came to Moses and said, “We, your servants, have accounted for all the men who went out to battle under our command; not one of us is missing! So we are presenting the items of gold we captured as an offering to the Lord from our share of the plunder—armbands, bracelets, rings, earrings, and necklaces. This will purify our lives before the Lord and make us right with him.
After purification ceremonies and the like, of fighting men and their gifts, the gifts ended up in the Tabernacle:
Numbers 31:54 So Moses and Eleazar the priest accepted the gifts from the generals and captains and brought the gold to the Tabernacle as a reminder to the Lord that the people of Israel belong to him.