Arab messengers played a vital role in the medieval Islamic world and its diplomatic relations with foreign powers. An innovative treatise from the 10th Century ("Rusul al-Muluk", "Messengers of Kings") is perhaps the most important account of the diplomacy of the period, and it is here translated into English for the first time. "Rusul al-Muluk" draws on examples from the Qur'an and other sources which extend from the period of al-jahiliyya to the time of the 'Abbasid caliph al-Mu'tasim (218-227/833-842). In the only medieval Arabic work which exists on the conduct of messengers and their qualifications, the author Ibn al-Farr rejects jihadist policies in favor of quiet diplomacy and a pragmatic outlook of constructive realpolitik. "Rusul al-Muluk" is an extraordinarily important and original contribution to our understanding of the early Islamic world and the field of International Relations and Diplomatic History.