Born several centuries later, Carl Von Clausewitz, and Antoine-Henri Jomini, further developed these concepts of warfare and statecraft but drew very different conclusions on waging war from their experiences serving in the Napoleonic Wars.
Jomini was a clear proponent of war as a science that was governed by timeless and well-developed principles. His work The Art of War, was written in a very precise and scientific manner, proposing concrete actions for a commander to take in given situations-“War is always to be conducted according to the great principles of the art; but great discretion must be exercised in the nature of the operations to be undertaken which should depend upon the circumstances of the case.”  Jomini does an admirable job of offering an early delineation of Strategy, Operational Art and Tactics, but still provides a checklist approach to battle that, while useful on a tactical or even operational level, does not take into account the political or diplomatic elements of war at the strategic level. Jomini’s entire thinking on warfare can be summed in his ‘fundamental principle of war’ which states- “To throw by strategic movements the mass of an army successively upon the decisive points of a theater of war and also upon the communications of the enemy as much as possible without compromising one's own.” 
Jomini’s thinking on the art or science of war was not as sophisticated or as complete as Sun Tzu’s or Clausewtiz’ on the political and diplomatic relationship to strategy and warfare. Moreover, although Jomini was an enthusiastic proponent of his self-described principles of war, as well as his concept of using ‘interior lines’ to conduct offensive operations, he did not clearly proscribe under what circumstances to apply which principle, in a sense contradicting his own ideas of war waged by fixed scientific principles. 
Clausewitz was probably the greatest of the classic strategic thinkers and incorporated a holistic view of war that remains both relevant and confusing today. As a member of the defeated Prussian military in 1806, Clausewitz shared Sun Tzu’s and Machiavelli’s viewpoints on the importance of the study and preparation for warfare to the survival of the state. Clausewitz very much considered war more of an art than science and did not subscribe to any particular set-piece solution for a tactical or strategic problem—“In short, absolute, so-called mathematical, factors never find a firm basis in military calculations…in the whole range of human activities, war most closely resembles a game of cards.” 
Clausewitz clearly understood that warfare was a very human interaction since armies and their commanders rarely remain static in their thinking and actions. The constant action and reaction of opponents in combat make a scientific approach to warfare very problematic and required a commander to exercise his ‘genius’ on a battlefield to overcome the friction and uncertainty of the battlefield. Clausewitz famous dictum of the ‘friction’ of combat that prevents a commander from exercising total control over a battlefield remains true today. Clausewitz and Sun Tzu both exhibited keen insights into the psychological aspects of warfare and Clausewitz in particular wrote extensively on topics such as the ‘genius’ or intuition of a commander to handle uncertainty, fear, bad information, and the basic confusion of a battlefield and still prevail. 
All of the author’s agree that at the tactical level there are definite ‘principles’ that apply to the successful conduct of battle such as discipline, use of terrain, the role of deception and surprise, simplicity and concentration of force. At the operational and certainly at the strategic level, the authors have some significant differences, which are never really reconciled, particularly the relationship between politics, diplomacy and military action and the interplay between generals and rulers.
History and even current American doctrine would seem to indicate that at the tactical level, there are certain ‘scientific’ principles that apply to combat. The employment of tanks, artillery, air power, and other modern weapons systems, particularly when combined with modern sensors and information systems would seem to make warfare an overwhelmingly technical and scientific activity that would eliminate Clausewitz’s ‘fog of war’. However, at the strategic and even operational level, war remains very much still an art. The U.S. Army’s current Field Manual 3-0 states- “Commanders use operational art to envision how to create conditions that define the national strategic end state. Actions and interactions across the levels of war influence these conditions. These conditions are fundamentally dynamic and linked together by the human dimension, the most unpredictable and uncertain element of conflict. The operational environment is complex, adaptive, and interactive. Through operational art, commanders apply a comprehensive understanding of it to determine the most effective and
efficient methods to influence conditions in various locations across multiple echelons.” 
Because warfare is always fought between people that react and adapt, there is likely never going to be a completely scientific approach to war. Technology cannot replace the thinking and reacting that a good battlefield commander brings to a conflict and as long as warfare is conducted between human opponents, war will remain more an art than a science.
 Antoine Henri Jomini, "The Art of War," Google Books, 1862, http://books.google.com/books?id=nZ4fAAAAMAAJ&printsec=frontcover&source=gbs_navlinks_s#v=onepage&q=&f=false (accessed Oct 2009), 15.
 Jomini, 70.
 John Shy, "Jomini," in Makers of Modern Strategy: From Machiavelli to the Nuclear Age, 143-185 (Princeton, NJ: Princeton University Press, 1986).
 Carl Von Clausewitz, On War, trans. Michael Howard and Peter Paret (Princeton, NJ: Princeton University Press, 1976), 86.
 Clausewitz, 100-102, 148-150; Peter Paret, "Clausewitz," in Makers of Modern Strategy: From Machiavelli to the Nuclear Age, 186-216 (Princeton, NJ: Princeton University Press, 1986); Michael I Handel, Masters of War: Classical Strategic Thought, 3rd (New York, NY: Frank Cass Publishers, 2001), 26-27.
 Headquarters, Department of the Army, "Field Manual (FM) 3-0: Operations," Joint Electronic Library, Feb 2008, http://www.dtic.mil/doctrine/doctrine.htm (accessed July 2009), 6-4.