Al-Anfal: 48
{ And [remember] when Satan made their deeds seem fair to them... }
[Remember] when Satan made their deeds—which they committed in opposing the Messenger of Allah (peace be upon him)—seem fair to them. He whispered to them that they would not be overcome and could not be resisted. He deluded them into thinking that following the footsteps of Satan and obeying him would provide them protection.
When the two armies met, Satan retreated and disowned them. That is, his plot became void when the soldiers of Allah descended. Thus said al-Hasan (may Allah have mercy on him): This was by way of whispering, and he did not manifest himself to them in physical form.
It is also said: When the Quraysh gathered to march, they remembered the war that existed between them and the Banu Kinana, which was holding them back. So, Iblis appeared to them in the form of Suraqa bin Malik bin Ju'sham, the Kinani poet—who was one of their nobles—accompanied by a host of devils carrying a banner. He said, "No one can overcome you today, and I am your protector against the Banu Kinana." But when he saw the angels descending, he retreated.
It is said that his hand was in the hand of al-Harith bin Hisham. When he retreated, al-Harith said to him, "Where are you going? Are you abandoning us at this moment?" He replied, "I see what you do not see," then he shoved al-Harith in the chest and fled. They were defeated. When they reached Mecca, they said, "Suraqa defeated the people." When this reached Suraqa, he said, "By Allah, I did not even know of your march until your defeat reached me." When they later embraced Islam, they realized it was Satan.
In the Hadith: "Iblis was never seen smaller, more defeated, or more enraged than on the Day of Arafah, due to what he sees of the descent of mercy—except for what was seen on the Day of Badr."
If you ask: Why was it not said la ghaliban lakum (no one overcoming you), as one says la dariban zaydan 'indana (no one hitting Zayd is with us)?
I reply: If lakum (for you) were the object of ghalib (overcoming)—meaning "no one overcoming you"—then it would be as you said. However, it is a predicate, with the estimation: "No overcomer is [existing] for you."
{ When the hypocrites and those in whose hearts is a disease said, "Their religion has deluded these people." And whoever relies upon Allah—then indeed, Allah is Exalted in Might and Wise. }