The participants had to be of Greek blood, for the origin of the games lay in religious ritual. 'Barbarians', non-Greeks, could not worship in the sanctuary of Zeus and could not take part in the games. Heralds travelled to the furthest outposts of Greek civilisation to invite the Greeks to take part. From Sicily and Cyrene, from Syria and Egypt, from Macedonia and Asia, they flocked to Olympia and, while the games were in progress, it was an honoured tradition that war should cease between Greek states.