(anc. geog.) a town in Judea, to the north of Jericho, called Ain by Josephus, and the inhabitants Ainata. Joshua having sent a detachment of 3000 men against Ai, God permitted them to be repulsed on account of Achan's sin, who had violated the anathema pronounced against the city of Jericho. But after the expiation of this offence, God commanded Joshua (chap. viii.) to march with the whole army of the Israelites against Ai, and treat this city and the kingdom thereof as he had treated Jericho, with this difference, that he gave the plunder of the town to the people. Joshua sent by night 30,000 men to lie in ambush behind Ai; having first well instructed those who had the command of them in what they were to do; and the next day, early in the morning, he marched against the city with the remainder of his army. The king of Ai perceiving them, fell hastily out of the town with all his people, and fell upon the forces of the Israelites; who upon the first onset fled, as if they had been under some great terror.

As soon as Joshua saw the enemy all out of the gates, he raised his shield upon the top of a pike, which was the signal given to the ambuscade; whereupon they immediately entered the place, which they found without defence, and set fire to it. The people of Ai perceiving the smoke ascending, were willing to return, but discovered those who had set fire to the city in their rear, while Joshua and those who were with him turning about, fell upon them, and cut them in pieces. The king was taken alive, and afterwards put to death.

The chevalier Folard observes, that Joshua's enterprise on Ai, excepting in some particulars of military art, is very like that of Gibeal, which is scarce anything more than a copy of it. It would appear, says that writer, by the scripture account, that Joshua was not the author of the stratagem made use of by him: for when God directs himself to Joshua, he says, "Go up against Ai; lay an ambuscade behind the town; I have delivered the king and the people of it into thine hands;" yet notwithstanding this, God might leave the whole glory of the invention and execution of it to him, as to a great general. "Joshua arose," says the sacred author, "and all the people of war, to go up against Ai (verse 3.)"; and Joshua chose out 30,000 mighty men of valour, and sent them away by night."

Folard remarks, that there is a manifest contradiction between this verse and the 12th, wherein it is said, that Joshua chose out 5000 men, whom he sent to lie in ambush, between Bethel and Ai. How is this to be reconciled? Calmet says, that Manus allows but 5000 men for the ambuscade, and 25,000 for the attack of the city, being persuaded that an army of 600,000 men could only create confusion on this occasion, without any necessity for, or advantage in, such numbers; but the generality of interpreters, continues Calmet, acknowledge two bodies to be placed in ambuscade, both between Bethel and Ai; one of 25,000, and the other of 5000 men.

With regard to the signal Joshua made to that part of his army which lay in ambuscade, the learned Folard embraces the opinion of the Rabbins, who believe what is called the shield to be too small to serve for a signal: hence they make it to be the staff of one of their colours: from this, our author concludes, that the whole colours were used on the occasion; for in the Asiatic style, which is very near the poetical, the part is oftentimes to be taken for the whole.