Terrorism analysts recognize the serious difficulties involved in identifying the 'causes' of terrorism. In addition to the transnational terrorism, there are a wide variety of groups whose aspirations are more limited in scope. These groups target single states, and although they may operate across borders, their attention is more narrowly focused. The cases are too numerous to be included in the brief history of terrorism. Despite the appearance of terrorist violence at various times in the distant past, modern terrorism is widely believed to have begun during the last third of the 19th century. Since that era, terrorist activity appears to have come in a succession of 'waves'. Anarchist activity in France represents a transition from terrorist attacks on single individuals to attacks carried out on a largely indiscriminate basis. Throughout the Russian Empire, independent groups, including Polish, Armenian, Ukrainian and Jewish groups, carried out a large number of attacks all aimed at liberation from the yoke of czarist oppression.