While NATO has kept Western Europe free from the use of military force or pressure, the rest of the world has unfortunately been— and seems likely to continue to be—the scene of considerable resort to the use of force and threats. Some of it has had to do with the end of colonialism, and still more with the subsequent internal power struggles in the emerging countries. Problems of development, growth and social change account for a goodly share of incidents. Ancient rivalries between neighbors are another fertile source of hostilities.