Or Bethel - See the Joshua 8:1 note.

There was not a man left in Ai or Beth-el - It is very likely that the principal strength of Beth-el had been previously brought into Ai, as the strongest place to make a stand in; Beth-el being but about three miles distant from Ai, and probably not greatly fortified. Therefore Ai contained on this occasion all the men of Beth-el - all the warriors of that city, as well as its own troops and inhabitants. Others think that the Beth-elites, seeing the Israelites fly, sallied out of their city as against a common enemy; but that, finding the men of Ai discomfited, and the city taken, they returned to Beth-el, which Joshua did not think proper to attack at this time. From Judges 1:24 we find that Beth-el was then a walled city, in the hands of the Canaanites, and was taken by the house of Joseph.

And there was not a man left in Ai or Bethel that went not out after Israel,.... For as these two places were very near to each other, but a mile apart, they were in confederacy, and acted together, and could easily be called to the help of each other when required: though there is a difficulty how the men of Bethel could join those of Ai, when the ambush lay between them both, Joshua 8:12; they either went another way, or the ambush purposely let them pass, for fear of a discovery by a skirmish with them, and that Bethel as well as Ai might be cleared of its armed inhabitants, and so fall an easy prey to them as well as Ai: this must be understood only of men of war; for otherwise there were inhabitants left, as old men, and such as were unfit for war, afterwards slain, Joshua 8:24,

and they left the city open: they did not stay to shut the gates, nor left porters or any guards about, to take care of, protect, and defend the city:

and pursued after Israel; with great eagerness and vehemence, not having the least apprehension of their city being in any danger.

And there was not a man left in Ai or Bethel, that went not out after Israel: and they left the city open, and pursued after Israel.

8:17 Not a man - Namely, fit for war. Bethel - Which, being a neighbouring city, and encouraged by the former success, had sent some forces to assist them; and now, upon notice sent to them of the flight of their common enemies, or upon some other signal given, all their men of war join with those of Ai in the pursuit.

8:3-22 Observe Joshua's conduct and prudence. Those that would maintain their spiritual conflicts must not love their ease. Probably he went into the valley alone, to pray to God for a blessing, and he did not seek in vain. He never drew back till the work was done. Those that have stretched out their hands against their spiritual enemies, must never draw them back.