وَإِنِ اشْتَدَّ الْخَوْفُ صَلَّوْا رُكْبَانًا وَوُحْدَانًا، يُومِئُونَ بِالرُّكُوعِ وَالسُّجُودِ إِلَى أَيِّ جِهَةٍ شَاءُوا إِذَا لَمْ يَقْدِرُوا عَلَى التَّوَجُّهِ إِلَى الْقِبْلَةِ
Translation: If fear becomes extreme, they may pray while mounted or individually, indicating bowing and prostration by gesture, and face whichever direction is possible when they cannot face the qiblah.
When the two-group arrangement itself becomes impracticable, prayer is performed individually, including on mounts and through head gestures. The inability to perform regular bowing and prostration is significant.
Facing the qiblah remains the normal requirement, but is relaxed when genuine danger makes it impossible.