The Peace of Westphalia treaty, 1648, is considered a watershed event in traditional geopolitics. It led to the creation of the modern nation-state system by allowing hegemons to connect their power to discrete, definable territorial units for the first time in history. As the system was concretized and formalized, it also paved the way for inter-state struggles for power. See Gallaher, in C. Gallaher et al. (2009).