Salim b. ‘Abdallah b. ‘Umar quoted his father as saying

I went on an expedition with Allah's Messenger ﷺ to Najd, and when we came in front of the enemy we drew up in line facing them. Allah's Messenger ﷺ then stood up and led us in prayer, and one section stood up along with him while another faced the enemy. He prayed a rak'a with those who were with him and made two prostrations, and then they changed places with those who had not prayed. When they came Allah's Messenger ﷺ prayed a rak'a with them and made two prostrations, then he uttered the salutation and each of them got up and left, after which he prayed a rak'a alone and made two prostrations. Nafi‘ transmitted something similar, adding that when there was greater cause for fear than on that occasion they prayed standing on their feet or mounted, without considering whether or not they were facing the qibla. Nafi‘ said he thought Allah's Messenger ﷺ was the one on whose authority Ibn ‘Umar mentioned that. Bukhari transmitted it.