Fleeing from Battle is prohibited, and its Punishment

Allah said, while warning against fleeing from the battlefield and threatening those who do it with the Fire,

يَـأَيُّهَا الَّذِينَ ءَامَنُواْ إِذَا لَقِيتُمُ الَّذِينَ كَفَرُواْ زَحْفاً

The exception covers two states: (1) لَّا مُتَحَرِّ‌فًا لِّقِتَالٍ أَوْ مُتَحَيِّزًا إِلَىٰ فِئَةٍ (unless maneuvering for battle,) (2) أَوْ مُتَحَيِّزًا إِلَىٰ فِئَةٍ (or turning to join a company) that is, when a war is on, turning one's back is permissible only under two conditions. Firstly, this turning back from the battlefield should simply be strategic, just to hoodwink the enemy and certainly not to bolt away from the battlefield in reality. In short, the purpose in sight should be to launch a blitzkrieg or a lightning attack on the enemy by making them complacent about what may look like a real retreat. This is the meaning of the statement: إِلَّا مُتَحَرِّ‌فًا لِّقِتَالٍ (unless maneuvering for battle) because the word: تَحَرُّف (taharruf) is used to refer to turning away towards a certain side obliquely. (Ruh al-Ma` ani)

The second state of exception in which it is permissible to turn one's back from the battlefield is that one realizes the weakness of one's combating force and moves back to gather additional support from Mujahidin and come back into the battle with added strength. This is what the sentence: أَوْ مُتَحَيِّزًا إِلَىٰ فِئَةٍ (or turning to join a company) means because the word: تَحَیُّز (tahayyuz) literally means to join up and فِئَةٍ (fi'ah) signifies a group, company or force. Thus, the sense is that should one back out from the battlefield with the intention of joining up with one's group, assembling the needed fighting support and returning to attack again, then, this is permissible.