[The large Persian formations] were analogous to a set of pillows, almost: big and voluminous, but not capable of (or willing to) exert much force. Mostly they fled before the Greeks, and avoided combat everywhere except in the intense fight when Cyrus charged the King. There only were the picked loyalist men of the two leaders fully engaged in brutal combat.I think the reason for this is that the Persian army has the same loyalty problem that Cyrus has with his native forces. They didn't come to fight; nobody wants to die for the Persian king. They came to show up in order to make a showing of loyalty to their best-guess about who was going to win, or the one they obtained sufficient benefits from that they couldn't not show up for them when called.
The King is not in a very happy position. He knows that the Greeks drove all his forces before them all day yesterday. He knows that his people aren't eager to die for him. He further knows that the Greeks will fight to the knife because they know that the alternative is torture if they happen to survive. So he has a morale problem in spite of his vastly superior numbers; and he has the problem that, if he attacks and is driven off or savaged by them, it will destabilize his rule and the appearance of strength on which it rests. It is so clear to him that this is an unhappy position that he withdraws his forces across the Tigris (thus further emphasizing how close we are to modern Baghdad, so close to both the great rivers).
The discussion of whether or not to surrender their arms involves some straightforward Greek philosophy, all of which points to keeping the arms. That section is enjoyable reasoning and shows practical wisdom in a state of difficulty.
"Conquerors do not, as a rule, give up their arms" [Meaning that the Greeks had whipped all Persians yesterday -- Grim]...
Cleanor the Arcadian, by right of seniority, answered: "They would sooner die than give up their arms." Then Proxenus the Theban said: "For my part, I marvel if the king demands our arms as our master, or for the sake of friendship merely, as presents. If as our master, why need he ask for them rather than come and take them? But if he would fain wheedle us out of them by fine speeches, he should tell us what the soldiers will receive in turn for such kindness." ...
Theopompus the Athenian spoke. "Phalinus," he said, "at this instant, as you yourself can see, we have nothing left but our arms and our valour. If we keep the former we imagine we can make use of the latter; but if we deliver up our arms we shall presently be robbed of our lives. Do not suppose then that we are going to give up to you the only good things which we possess. We prefer to keep them; and by their help we will do battle with you for the good things which are yours." Phalinus laughed when he heard those words, and said: "Spoken like a philosopher, my fine young man, and very pretty reasoning too..."
Clearchus said "The sight of you, Phalinus, caused me much pleasure; and not only me, but all of us, I feel sure; for you are a Hellene even as we are--every one of us whom you see before you. In our present plight we would like to take you into our counsel as to what we had better do touching your proposals. I beg you then solemnly, in the sight of heaven--do you tender us such advice as you shall deem best and worthiest, and such as shall bring you honour of after time, when it will be said of you how once on a time Phalinus was sent by the great king to bid certain Hellenes yield up their arms, and when they had taken him into their counsel, he gave them such and such advice. You know that whatever advice you do give us cannot fail to be reported in Hellas."
Clearchus threw out these leading remarks in hopes that this man, who was the ambassador from the king, might himself be led to advise them not to give up their arms, in which case the Hellenes would be still more sanguine and hopeful. But, contrary to his expectation, Phalinus turned round and said: "I say that if you have one chance, one hope in ten thousand to wage a war with the king successfully, do not give up your arms. That is my advice. If, however, you have no chance of escape without the king's consent, then I say save yourselves in the only way you can." And Clearchus answered: "So, then, that is your deliberate view? Well, this is our answer, take it back. We conceive that in either case, whether we are expected to be friends with the king, we shall be worth more as friends if we keep our arms than if we yield them to another; or whether we are to go to war, we shall fight better with them than without."
So, no. You will not be getting our arms. Nor does the King attempt to do so.
The Greeks withdraw to rejoin their native allies, and then decide to strike off north because they already know the way they came has no food upon it. They shortly come upon the outliers of the King's army, who withdraw further before them. The King is so eager to be rid of them that he sends another embassy to discuss further options. After a further discussion Tissaphernes proposes to lead them safely out of Persia, arranging for them to purchase food along the way in return for their promise not to raid the countryside or wage war upon it. He then keeps them there for 20 days while preparing for his own journey, during which time the Greeks suspect treachery is brewing but choose to wait for the promised escort instead of having to fight all the long way out.