For fifty years debate has raged about early European commerce during the period between antiquity and the middle ages. Was there trade? If so, in what – and with whom? New evidence and new ways of looking at old evidence are now breaking the stalemate. Analysis of communications – the movements of people, ideas and things – is transforming our vision of Europe and the Mediterranean in the age of Charlemagne and Harun al Rashid. Michael McCormick is the Francis Goelet Professor of Medieval History Chair, Science of the Human Past at Harvard University.