Abdullah ibn Umar
Ibn Isfandiyar narrates that during the caliphate of Umar, Hassan, along with Abdullah ibn Umar and an army of Kufis, was present in the campaign towards Amol in Tabaristan. Wilferd Madelung believes that Ali probably wanted to expose Hassan early to war and add to his experiences. Some Shia scholars like Ja'far Murtaza Al-Ameli have questioned this story and given reasons for its inaccuracy.