What was the first battle witnessed by the Messenger of Allah, may Allah bless him and his family and grant them peace?

The first غزوة (military expedition) undertaken by the Prophet, peace and blessings be upon him, was the Ghazwat al-Abwa'. Imam al-Bukhari titled a chapter in his Sahih (Book of Military Expeditions) as: "Chapter: Ghazwat al-'Ushayra or al-'Usayra. Ibn Ishaq said: The first expedition the Prophet, peace and blessings be upon him, undertook was al-Abwa', then Buwat, then al-'Ushayra." As for what al-Bukhari and Muslim narrated from Zayd ibn Arqam, that the first expedition was al-'Ushayra, this is understood to mean that he was unaware of the expeditions of al-Abwa' and Buwat due to his young age at the time, or that it referred to the first expedition Zayd ibn Arqam participated in with the Messenger of Allah, peace and blessings be upon him. This expedition (al-Abwa') took place in Safar of the second year of the Hijra.