It happened, when all the kings of the Amorites, who were beyond the Jordan westward, and all the kings of the Canaanites, who were by the sea, heard how that Yahweh had dried up the waters of the Jordan from before the children of Israel, until we were passed over, that their heart melted, neither was there spirit in them any more, because of the children of Israel.
God had guaranteed Joshua’s success only as he kept the Mosaic Law (Joshua 1:7). It was necessary therefore that all the males who had been born in the wilderness and had not undergone circumcision should do so. Circumcision brought the individual male under the blessings of the Abrahamic Covenant (Genesis 17). It was also a prerequisite for partaking in the Passover that God required of all Israelites yearly (Exodus 12). Like the stones just set up, circumcision was also a memorial.