The Expeditions and battles of Hazrat Umar (ra)

Hazrat Umar (ra) bin Al-Khattab participated in all the battles alongside the Holy Prophet (sa), including the battles of Badr, Uhud and Khandaq. Apart from this, he also participated in a number of expeditions in which the Holy Prophet (sa) was not present, and in some of them, he was appointed as the commander of the army.

(Ibn Saad, Al-Tabaqat al-Kubra, Vol. 3 [Beirut, Lebanon: Dar al-Kutub al-Ilmiyyah, 1990], p. 206)