Border zones are incubators of criminal instability and violence. Weak state presence and the lucrative drugs trade is combining to challenge state sovereignty in acute ways. Consider Mexico, where the northern frontier with the US and southern border with Guatemala are contested zones. The bloody center of gravity of Mexico’s drug cartels is the ‘plazas’, the drug smuggling corridors that link the borders. When most think of conflict and border zones, they imagine territorial disputes such as India and Pakistan’s recurring battles over Kashmir or less serious tug-of-wars such as Japan and South Korea’s contestation of the Liancourt Rocks. To be sure, there have been territorial disputes, such as Nicaragua’s dispute with Colombia over several islands, or Colombia’s conflicts with Venezuela and Ecuador over narco-guerrillas operating from their territory. Yet, as former FRIDE researcher Ivan Briscoe argues, the biggest sources of violent conflict has been the erosion of government control over border zones and the rise of criminal groups, gangs, and cartels in loosely governed zones. As Briscoe argues, "violence and institutional corrosion have plagued as never before the frontier between Mexico and the United States, while Guatemala’s eastern border region and Colombia’s frontiers with Ecuador, Venezuela and Brazil witness these countries’ highest murder rates, as well as territorial capture by armed groups and narco-trafficking networks."