As the world is moving into the third decade of the 21st century, it is ever more filled with uncertainties and complexities per se. The scope of security agencies has grown beyond just protecting the state from external and internal security threats. Instead, military forces have to face a whole new domain of security challenges, unlike those from a few centuries ago. Irregular and hybrid warfare has replaced the conventional way of battlefield confrontation between the state armies. The global rise in insurgency, terrorism, civil wars, failed states, and humanitarian crises have made the security landscape even more volatile. In this context, modern problems require modern solutions. However, most of these contemporary solutions to our security challenges can be traced back to classical war philosophies. This article attempts to explain the emerging forms of conflicts and irregular security threats, and how those war theories and strategies are more effective in managing them. It starts by reviewing the key ideas of selected classical military thinkers such as Sun Tzu, Machiavelli, Frederick II, Clausewitz, Jomini, and Liddell Hart. The latter part of the article discusses their present relevance and analyses recurring American experiences with low-intensity conflicts like insurgency and terrorism from the perspective of classical war philosophies. It is observed that the statesmen and military planners of today can still find inspiration in the age-old battlefield concepts, such as political-military relationship, intelligence, deception, indirect approach, battle avoidance, and center of gravity, to resolve conflicts and improve the condition of global peace.