Joshua 5:4

And [this is] the way in which Joshua purified the children of Israel; as many as were born in the way, and as many as were uncircumcised of them that came out of Egypt,

And this is the cause why Joshua did circumcise: All the people that came out of Egypt, that were males, even all the men of war, died in the wilderness by the way, after they came out of Egypt.

This is the reason Joshua circumcised them: all the people who came out of Egypt, who were males, even all the men of war, died in the wilderness along the way, after they came out of Egypt.