One of the most distinctive rituals of Roman imperial accession was the adlocutio, the speech delivered by the new emperor to a military assembly, which can be documented from the first to the fifth centuries a.d. This article seeks to explain the extraordinary endurance of this neglected genre of speech by examining its origins, setting and content. After outlining the unusual nature of the accession adlocutio when set against both earlier and contemporary Mediterranean practice, the first half of this article traces its origins to the military culture of the late Roman Republic. In particular, the adlocutio is related to two other rituals which rose to new prominence in the era of the Civil Wars: the acclamation of the victorious general as imperator and the granting of military gifts. In the second part of this article, the setting for the typical adlocutio of the Imperial era is discussed using the often-problematic evidence of our ancient historical sources. The content of the speech itself is then reconstructed primarily through a close reading of our one surviving example, the brief address of Leo I preserved by Peter the Patrician. Finally, the evidence for the origins and content of the speech are brought together in an argument for the speech's survival as a useful tool for emperors seeking to establish a permanent bond with the soldiers they commanded.