بسم الله الرحمن الرحيم

فَإِنۡ خِفۡتُمۡ فَرِجَالاً أَوۡ رُكۡبَانً۬ا‌ۖ فَإِذَآ أَمِنتُمۡ فَٱذۡڪُرُواْ ٱللَّهَ كَمَا عَلَّمَڪُم مَّا لَمۡ تَكُونُواْ تَعۡلَمُونَ

“But if you are in fear, then (pray) on foot or riding. But when you are in peace, recite Allah’s name as He has taught you what you did not know. (239)” 

Ruling: This verse has allowed a special way of offering prayers in the state of fear, i.e. the state of war. In such a state one can offer prayer while standing, on condition that he can stand in one place without moving, and can make the gesture of sajdah in a lower position than he makes in ruku. However, salaah cannot be performed while walking. It this case of fear, it is permissible to offer the salah while riding, as well as, through gestures. In both of these cases, salaah will be valid while not facing the qibla. (Maarif Al Quran V1 pg 612, Tafsir Uthmani V1 pg 254)