National security refers to the requirement to maintain the survival of the nation-state through the use of economic, military and political power and the exercise of diplomacy. The concept of security of a nation goes back to the dawn of nation-states themselves. Armies for domestic peacekeeping and maintaining national sovereignty have existed since the dawn of recorded history. Civil and national police forces have also existed for millennia. Intelligence agencies and secret services of governments stretch back to antiquity such as the Roman Empire's frumentarii and agents in rebus. While the general concepts of keeping a national security are not new, the specific modern English term "national security" itself came into common parlance in the 20th century. Methodologies to achieve and maintain the highest possible desired state of national security have been consistently developed over the modern period to this day. Others believe that the national security approach has outlived its usefulness to the international community since many of the sources of global insecurity today (such as terrorism or global warming) are immune to unilateral state military responses. In response to this growing sense of dissatisfaction, growing numbers of scholars, NGOs, and policy makers have argued for the adoption of a new people-centered model for human security. Human security argues that global security is best enhanced when state leaders focus on reducing human vulnerabilities as the best pathway to enhancing state security (Wikipedia).