Multi-ethnic societies, in contrast to single ethnic societies, integrate different ethnic groups irrespective of differences in culture, race, and history under a common social identity larger than one "nation" in the conventional sense. All cities and most towns can be regarded as multi-ethnic societies, even ones where race hatred and ethnic intolerance is common.
Also, many nations that today are considered ethnically homogeneous, such as Japan, have their origins in a more or less violent melting or mixing process.
There is a distinction between a society, a nation, a people, and a state. See multi-national state for the specific political and military issues arising from such a state. There is much overlap however between the concerns of running a state, and finding a common identity as a nation.

History

All Nations in the Americas
Afghanistan
Australia
Bosnia and Herzegovina
France
Germany
India
Iran ( different ethnic and religious groups)
Israel
Malaysia
New Zealand
Pakistan
Singapore
South Africa
United Kingdom Historic multi-ethnic societies

Belgium
Bosnia and Herzegovina
China
India
Iraq
Israel
Macedonia
Papua New Guinea
Philippines
Russian Federation
Sri Lanka
Switzerland
Vojvodina (in Serbia)
Almost all countries in Subsaharan Africa Preconditions for success
Due to their ethnic or cultural heterogeneity, multi-ethnic societies in general are more fragile and have a higher risk of conflicts. In the worst case such conflicts can cause the breakdown of these societies. Recent examples of this were the violent breakdown of Yugoslavia and the peaceful separation of Czechoslovakia. Forced mixture or coexistence of ethnically different populations might be the reason for the outbreak of nationalistic and racistic tendencies which over the years can become so strong that they are able to destruct a multi-ethnic society.