The precise delineation of boundaries is relatively new in human history. Before the availability of surveying and cartographic technologies, impediments to travel such as mountain ranges, water bodies, or even features such as broad as forests and deserts were used to separate the territories of political entities (Antecedent boundaries). In Europe, the 1648 Peace of Westphalia gave rise to a more territorially-based notion of the sovereign state, creating an imperative for the delineation and demarcation of boundaries and the establishment of border facilities (Subsequent boundaries).
The colonial expansion of European states in the 17th, 18th, and 19th centuries led to the creation of many international boundaries that endure to this day, even though they were often drawn arbitrarily (Superimposed boundaries). As recently as the late 19th century, European powers delineated boundaries on the map of Africa without surveys on the ground and without regard to the economy or culture of African people. Until the second half of the twentieth century, international boundaries were subject to change arising from diplomatic agreements and military conflict.
In the years following World War II, an international consensus arose around the territorial integrity norm, a principle that in order to prevent armed conflict, existing boundaries should be treated as unchangeable. While this has led to the preservation of colonial-era boundaries that have negatively impacted economic and cultural development in Africa, the frequency of wars over territory has declined. This does not mean that the political map has remained unchanged. The disintegration of states, including the Soviet Union and Yugoslavia, into multiple smaller states, has created new international boundaries within pre-existing boundaries. At the same time, the German reunification in 1991 involved the dissolution of a boundary that has divided Europe for decades (Relic boundaries).