Battle of Khaybar
After signing the truce, Muhammad assembled an expedition against the Jewish oasis of Khaybar, known as the Battle of Khaybar. This was possibly due to housing the Banu Nadir who were inciting hostilities against Muhammad, or to regain prestige from what appeared as the inconclusive result of the truce of Hudaybiyya. According to Muslim tradition, Muhammad also sent letters to many rulers, asking them to convert to Islam (the exact date is given variously in the sources). He sent messengers (with letters) to Heraclius of the Byzantine Empire (the eastern Roman Empire), Khosrau of Persia, the chief of Yemen and to some others. In the years following the truce of Hudaybiyya, Muhammad directed his forces against the Arabs on Transjordanian Byzantine soil in the Battle of Mu'tah.