Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: I went on a campaign with the Prophet (peace and blessings be upon him) towards Najd. We met the enemy and formed ranks against them. Then the Prophet (peace and blessings be upon him) stood and led us in prayer. One group stood with the Prophet (peace and blessings be upon him) and the other group faced the enemy. The Messenger of Allah (peace and blessings be upon him) bowed and led those who were with him (peace and blessings be upon him) in one rak'ah with two prostrations. Then they turned away and went to the place of those who had not prayed, and the group that had not prayed came. Then he (peace and blessings be upon him) led them in one rak'ah. Then the Messenger of Allah (peace and blessings be upon him) gave the salam, and every man stood up and performed one bowing and two prostrations by himself.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6039
Salim bin Abdullah bin Umar (may Allah have mercy on him) narrates from his father (Sayyiduna Abdullah bin Umar (may Allah be pleased with them both)) that the Prophet (peace and blessings be upon him) led one of the two groups in one rak'ah while the other group was facing the enemy. Then they left and stood in the others' place. Then the other group came, and he (peace and blessings be upon him) led them in one rak'ah. Then he (peace and blessings be upon him) gave the salam. Then these stood up and completed their rak'ah, and the others completed their rak'ah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6040
Nafi' narrates from Ibn Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) led the fear prayer: one group stood with him (peace and blessings be upon him) and the other group faced the enemy. He (peace and blessings be upon him) led them in one rak'ah. Then these went to the others' place and those came to their place. Then he (peace and blessings be upon him) led them in one rak'ah. Then he (peace and blessings be upon him) gave the salam. Then both groups each completed their own one rak'ah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6041