The Greek city-states, for example, despite frequent wars, formed an international society with a common language, common traditions, and some common religious practics such as a respect for the Delphic oracle and participation in the Olympic Games. Although they never formed any stable federation, they distinguished themselves as Greeks from 'barbarians' (which meant,in the first instance, people who spoke a foreign language). In some degree this affected their behavior. For example, they were prepared to make slaves of conquered barbarians but not, usually, of conquered Greeks.