Henri Jomini and Carl Von Clausewitz were prominent military thinkers in the 19th century. Much of their writings were based on the wars fought by Napoleon and Frederick the Great. Both Jomini and Clausewitz were first hand witnesses to the military exploits of the aforementioned generals.
Both military theorists, Clausewitz and Johmini wrote about the Napoleonic era wars, their publications contained significant differences. Clausewitz is almost in a metaphysical mode in his publication of ON War. He assumes the reader is already familiar with Henri Johmini. Johmini expressed his view on the geometrical rules for warfare. With that said, perhaps the most significant differences between them were their views on the relative power of offensive and defense. Clausewitz clearly emphasizes the power of tactical defense, while Johmini leans toward tactical offensives.
Both of them based their works on the experience made fighting during the Napoleonic wars and by reading Napoleon's writings. Indeed ,only Clausewitz was able. to catch the "living gist", the "significance" implied in the experience made by the great leader, without reduce it in a series of pedantic "rules", good for all kind of purposes.
The primary early 19th century military theorists Henri Johmini and Carl von Clausewitz had similar but not exactly the same ideas on military strategies and tactics. Their similarity comes from the fact that both of them had a keen interest in the military campaign of Frederick the Great. Also, each had personal experiences in the Napoleonic War Era. And, lastly, they learned from each other by reading each other's books.
There were a number of European military theorists besides Henri Jomini. A popular publication on warfare came from one of Napoleon's field marshals. Auguste de Marmount's Spirit of Military Institutions also had merit for its time. Marmont urged readers to only read publications on warfare from officers who actually fought battles as he did under Napoleon. Other authors, such as Carl Von Clausewitz, had yet to be translated from German.
Vladimir Lenin decided to read the works of Carl Von Clausewitz in 1915. Lenin was in exile at the time and World War One was raging. Lenin believed he needed a better education on wars and the publication called "On War" by Clausewitz was an excellent source on such matters.
After the Union victory at the Battle of Shiloh, General Halleck made a remarkable 150 mile advance into Confederate territory. Based on several negative factors such as advancing within the enemy's homeland, neither military theorists Clausewitz or Johmini never would have believed a rapid advance would be possible. These men failed to take into consideration the fact that by using waterways and gunboats, Halleck was able to make a rapid advance.
Henri Jomini believed that the best way to study and formulate ideas concerning the art and science of military operations was to study and or be a part of ongoing military campaigns. He for example based his military publications on his real life experiences on the field of battle as a participant or observer.
In his book called On War, Carl von Clausewitz presents his theory that there are three forces that drive a war. The form a trinity he calls chance, passion, and rationality. This should not be confused with his ideas on war itself. Here in his trinity he speaks in very broad terms.
The relevance of Carl Von Clausewitz's "Principles of War" for contemporary military professionals is that it deals with the mind of man at war and not the weapons of war.
Perhaps the two most referred to military authorities on 19th Century warfare, Henri Jomini and Carl von Clausewitz had slightly different views on political appointments to generalships that may apply to the US Civil War. Jomini studied the US Civil War and he opposed political appointments that both presidents Lincoln and Davis made. Some readers of both military theorists claim that Clausewitz would have understood it based on his argument that policy creates war, and the US Civil War was the result of political policies. There was, however, agreement between these theorists on this: That generals were made not born. There was nothing to prevent a politician, with the necessary attributes and study of warfare to become a capable general. US Civil War political appointees however, were not much inclined to study warfare before engaging the enemy.
As with most nations' military, strategies and tactics in any ongoing conflict are not publicized, however, observers can make assessments as they see military operations unfold. And, Army doctrines can be ignored if the circumstances do not fit doctrine. It can be said however, that military students and their professors discounted Carl Von Clausewitz until 1984. Curriculum changes however, can be dull to most people. With that said, US Army officers discuss the works of Clausewitz and his ideas on culminating points and centers of gravity with serious thought, both for historical purposes and where they may be applied to future military conflicts. They. however, are not as of yet, Army doctrines.
One major difference between Carl Von Clausewitz and Henri Johmini is the fact that Clausewitz writes more on how politics and military strategies are linked. Johmini tends to shy away from this angle of warfare and is more concerned with purely military tactics and strategy. As an aside, Vladimir Lenin studied Clausewitz because Clausewitz speaks to what Lenin wanted to learn. That being how military strategies and political goals are inter related.