There are instances according to Islamic tradition where Muhammad is thought to have sent letters to other heads of state during the Medinan phase of his life. Personalities, amongst others, included the Negus of Axum, Heraclius (emperor of the Byzantine Empire), the Muqawqis of Egypt, Khosrau, Sassanid King of Persia (Iran). There has been great controversy amongst academic scholars as to their authenticity.[42] According to Forward, academics have treated some reports with scepticism, although he argues that it is likely that Muhammad had assumed correspondence with leaders within the Arabian Peninsula.[4] R.B. Serjeant opines that the letters are forgeries and were designed to promote both the 'notion that Muhammad conceived of Islam as a universal religion and to strengthen the Islamic position against Christian polemic.'