When does jihad become individually obligatory upon those present in battle?

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Jihad becomes individually obligatory upon every Muslim present when two armies meet and their ranks are drawn up for battle. Retreat is forbidden for those who witness this confrontation, and remaining steadfast becomes mandatory for them. This ruling is supported by the Divine Command: O you who have believed, when you meet a company [of the enemy], stand firm and remember Allah much (Quran 50:45), and His statement, Be patient; indeed, Allah is with the patient (Quran 50:46). Furthermore, the prohibition against turning one's back is absolute, as stated in: O you who have believed, when you meet those who disbelieve advancing in array, do not turn to them [in retreat] (Quran 8:15). Whoever turns his back to them on such a day—unless maneuvering for battle or joining another detachment—has drawn upon himself wrath from Allah (Quran 8:16).