The Lord gave Lachish into the hands of Israel; and Joshua captured it on the second day, and struck it and every person who was in it with the edge of the sword, just as he had done to Libnah.
So the Rabshakeh returned and found the king of Assyria fighting against Libnah [a fortified city of Judah], for he had heard that the king had left Lachish.
and when the Lord your God gives them over to you and you defeat them, then you shall utterly destroy them. You shall not make a covenant (treaty) with them nor show mercy and compassion to them.
Now Joshua captured Makkedah on that day, and struck it and its king with the edge of the sword; he utterly destroyed it and everyone who was in it. He left no survivor. So he did to the king of Makkedah just as he had done to the king of Jericho. [Josh 6:21]
Joshua captured all the cities of these kings, and all their kings, and he struck them with the edge of the sword, utterly destroying them, just as Moses the servant of the Lord had commanded. [Deut 20:16]