This article surveys three important and interlinked aspects of Justinian's policy in his first decade: reconquest in the West; the establishment of a set of fundamental texts of Roman Law; and the achievement of unity of belief within the Church. In that context, it looks at the remarkable record preserved in Acta Conciliorum Oecumenicorum III, of five successive sessions of a synod held at Constantinople, and one synod in Jerusalem. Its purpose is both to illustrate contacts and influences across the Mediterranean and, more particularly, to bring out distinctive features of the Church in the Near Eastern provinces.