salam Israfeel
8:11 Sleep overcame you to give you tranquility from Him; and He sent down to you water from the sky to cleanse you with it and cause the affliction of the devil to leave you; and so that He may strengthen your hearts and set firm your feet.
8:12 Your Lord inspired to the angels: ?I am with you so keep firm those who believe. I will cast terror into the hearts of those who have rejected; so strike above the Aanak/necks, and strike from them every banan (/one standing).?
i don't think that 8:12 is speaking about any battle. I see no war in 8:12.
بن (مقاييس اللغة)
وإنما اشتقاق البَنَان من قولهم أبَنَّ بالمكان إذا قام؛ فالبنان به يُعْتَمَدُ كلُّ ما يكون للإقامة والحياة
so banan can be understood as any kind of habitation for resting or living.
i see no fingertips in 8:12.
above aanek is not on aanek. Above aanek there is the head wich contains brain, eyes, noses, mounth, ears...
if i read 8-11, action seems to happen during the night.
in 8-12, God tells angels to:
-keep firm those who believe.
-I will cast terror into the hearts of those who have rejected,so strike above the necks, and strike from them every one standing
the effect expected for "strike above the necks, and strike from them on banan" is to cast terror into hearts. Not to kill.
so 8-11 and 8-12 are speaking about the psychological preparation during the night before the war.
good "conditions" for believers, and "nightmares" or difficult meteorogical conditions (destroying habitations), frightening and whatever put terror in hearts of ennemies. That was the task af angels.
the war begins in 8:15 until 8-17
8:15 O you who believe; when you encounter those who have rejected on the battlefield, do not flee from them.....
that is how my rabb explained to me verse 8-12.
Peace