Adam Clarke on Joshua 1:14

Your wives, your little ones - And with these it appears, from Num 32:17, were left behind 70,580 effective men to guard them and their property; only 40,000 having passed over Jordan to assist the nine tribes and half to conquer the land. See Jos 4:13.

Armed - חמשים chamushim, by fives; in several lines, five in front, probably the usual method of marching; but it seems to signify arrayed, equipped, accoutred, well-armed, and ready for battle. See the note on Exo 13:18.