The Development of The Corps D'Armée And Its Impact on Napoleonic Warfare
The organization of the corps d'armée and the doctrinal use of the bataillon carré were significant in making the campaigns of Napoleonic warfare quicker and more fluid than those of Frederick the Great's time. These changes allowed Napoleon to hold a decisive advantage over his opponents until at least 1807.  The concepts upon which these two changes were made are still applicable today.
Jomini called the style of warfare conducted during the time of Frederick the Great a " ...system of positions..." and defined it as the "... the old manner of conducting a methodical war, with armies in tents, with their supplies at hand, engaged in watching each other; ..." . This style of warfare was characterized by campaigns of limited combat in which it was generally possible for an opponent to refuse combat if he so chose. One of the reasons for this was the organization of armies as single entities, concentrated for both movement and battle. In Frederick's time an army had no sub-structure higher than the regiment (3) and was therefore a pondering beast that generally moved along one route. Subdividing the army into separate regiments might allow an adversary to overwhelm the separate parts piecemeal. This concentration during movement caused the army to move slowly and allowed its opponent to determine, with relative ease, its objective. Supplying this type of army required huge depots, which tended to keep the army on a "short leash" from its supply base. . Monarchs were not willing to let these armies live off the land, and even if they were, it was impractical since a single route may not have sufficient food stuffs to support such a force. 
Napoleonic warfare was characterized by "...its limitless variation and flexibility."  Napoleonic warfare was quick and bloody, and sought a decisive engagement. Napoleon's army dispersed to move along separate routes and concentrated to fight. The French army of 1806 was not tied to large immobile depots for supplies, but lived off the land as it moved. This allowed the new armies to move, not only faster and farther, but to change direction quickly. Napoleon's "...insistence on speed and mobility was a basic feature of the Emperor's campaigns from beginning to end, and was the feature of his warfare that most confused and unsettled the majority of his opponents, brought up in a tradition that taught a more leisurely type of warfare."  The ability to disperse and concentrate rapidly, and to advance on several routes "...allowed Napoleon to do something Frederick's armies could never do--force engagement." 
Military thinkers were not idle during the period between the campaigns of Frederick the Great and the French Revolution and the rise of Napoleon. Writers proposing new theories of warfare were profuse during this time. Some of the most influential were advocating of a new type of warfare emphasizing mobility, the divisional organization of armies, and citizen armies possessed with a nationalistic zeal. These thinkers not only affected the makeup and doctrine of armies of the nineteenth century, as had the French Revolution, but they profoundly influenced the ideas of Napoleon, who would adapt and adjust them and then put them into practice.
Jacques Antoine Hypolite, Comte de Guibert was one of these influential military thinkers. He proposed the use of citizen armies which, because of their pride and courage, "...would have nothing to fear from the mercenary armies of other countries." He advocated the exploitation of mobility and declared that positions would necessarily become less important. More importantly for the subject at hand, Guibert called for the organization of armies into permanent divisions capable of supporting themselves to facilitate the necessary mobility.  Bonaparte "...read and reread the famous Essai général de Tactique ...which first appeared in 1772 when the author [Guibert] was only twenty-nine."  This concept "...of subdividing the armies into permanent, self-contained divisions" was not new "...and had first been actively practiced by Marshal Broglie during the Seven Years' War, .... In his 'Instruction of 1761,' Broglie enunciated the principles on which the Napoleonic divisional and corps systems operated." The system was discarded by the French after Broglie's death, but it became "an integral part of Guibert's teachings," and was revived in 1793. 
Another of these inter-war thinkers who influenced the development of Napoleon's corps d'armée system, was Jean de Bourcet. Bourcet's Principes de la guerre des montagnes emphasized the necessity of dispersal to force the enemy to cover many different points, and he called for marching in order of battle. The dispersal of forces during the march was to be followed by a rapid concentration of forces at the decisive point before the enemy could do the same. This allowed the attacker to begin with a significant advantage during the ensuing battle.  The following excerpt from Bourcet's writings could very well describe a Napoleonic campaign:
...a general will do well to divide his army into a number of comparatively small bodies, ...which ... is indispensable and safe provided the general who adopts it makes such arrangements that he can reunite his forces the moment that becomes necessary. He must therefore make his dispositions so that the enemy cannot interpose between fractions into which his army is divided...
A general who intends to take the offensive should assemble his army in three positions, distant not more than a march from one another, for in this way, while he will threaten all points accessible from any portion of the 25 or 30 miles thus held, he will be able suddenly to collect his whole army either in the centre or on either wing. The enemy will then be tempted to post troops to defend each of the threatened avenues of approach, and the attempt to be strong at all points will make him weak at each separate portion.
However carefully the enemy may have prepared his communications between several parts of his army, ...in case of an attack at any point he will not be able to concentrate his troops there in time, if only the attacking general has concealed his plan and his first movements. The attacking general will usually be able to steal a march, ...while the defender requires time to receive warning, time to issue orders, and time for the march of the troops to the point attacked. 
In 1800 Napoleon permanently organized the army into corps, the corps d'armée. This allowed him to use multiple routes of advance and increased his ability to live off the land, which freed him from the logistic constraints to which so many of his enemies were prisoner. This in turn permitted the French army to move fast and far, and to prevent the enemy from determining its true objective. The organization of the corps gave Napoleon protection from having his separated columns overwhelmed piecemeal. 
The corps was composed of all arms of the service, was self-sustaining, and could fight on its own until other corps could join in the battle. The corps itself was a headquarters to which units could be attached. It might have attached two to four divisions of infantry with their organic artillery, it had its own cavalry division and corps artillery, plus support units. With this organization a corps was expected to be able to hold its ground against, or fight off an enemy army for a least a day, when neighboring corps could come to its aid. "Well handled, it can fight or alternatively avoid action, and maneuver according to circumstances without any harm coming to it, because an opponent cannot force it to accept an engagement but if it chooses to do so it can fight alone for a long time." 
Finally the corps commander in Napoleon's army operated on mission type orders. He was expected to operate in a semi-autonomous mode using his "...own best judgment and experience, for the common strategic purpose." The corps commander followed standard procedures while maneuvering his unit. His general line of advance was dictated by the Emperor, but he was allowed full flexibility in choosing his march techniques and battle formations. Once engaged, he was in charge of his fight with the enemy, while the other commanders followed the standard procedure of marching to the sound of the guns unless instructed otherwise. 
The Grande Armée, composed of the various corps d'armée, could make use of several different strategic formations for an advance: echelon, with one wing refused; wedge; and en potencé, in which one flank was reinforced. The most striking doctrinal development which the corps d'armée allowed Napoleon to make use of, was his concept of advancing the army in a battalion square, the bataillon carré. The formation was simple yet offered "...infinite flexibility...."  In this formation the separate corps would march along parallel roads within one or two days march of each other. With an advance guard, a left flank, a right flank, a reserve corps, and an active cavalry screening force, the army provided itself with all round defense and could easily concentrate in any direction depending upon which corps made initial contact with the enemy. The front of an advancing bataillon carré might be as much as 120 miles. This system not only provided the French a degree of flexibility in operations not seen before, but was a key to deceiving the enemy as to his true objective.
The bataillon carré threatened the enemy with an attack from many directions and forced him to try to cover all avenues of approach. It also allowed Napoleon to force his opponents into combat, often before they were ready. It was not necessary to know the exact location of the enemy army because this operational dispersal of forces allowed Napoleon to find, and then fix the enemy with a portion of his army, while the other corps converged on their victim. Opposing commanders found it difficult at best, and usually impossible to maneuver out of the way of the advancing juggernaut. 
The effects of these changes in organization and doctrine were profound in making the campaigns of Napoleonic warfare quicker and more fluid than those of Frederick the Great's time. The changes allowed Napoleon to operate in an uncertain environment when the exact location of the enemy remained vague. "...it mattered little on what point of the compass the foe was discovered." His formation allowed him to engage the enemy in any direction with at least one corps, while the others converged on the battle.  It gave him infinite flexibility to change direction at once and concentrate anywhere within 24 hours making warfare much more fluid. Changing front was merely a matter of issuing orders or marching to the sound of the guns. The ability to move over several roads, find the enemy, change front and concentrate against him made it difficult for the enemy to avoid combat with Napoleon. This ability to force combat on his opponents, allowed Napoleon to gain the decisive battle he sought, and to bring the campaign to a rapid conclusion. This was a significant reason for the quickness of Napoleonic warfare.
These changes were fully revealed in the campaign of 1806 that resulted in the double battle of Jena-Auerstadt. On October 8 Napoleon began his advance through the Thuringian Forest to force the Prussian army to battle. He advanced in a bataillon carré of about 180,000 men in three columns of two corps each. The Cavalry Corps and the Imperial Guard followed the middle column and a division of Bavarians followed the right column. He was unaware of the exact location of the Prussian army, but was confident that his formation would allow him to find and fight the enemy on favorable terms. His front extended 200 kilometers when he began his advance. He shrank the front to 45 kilometers for the passage through the Thuringian Forest, and then he expanded it to 60 kilometers once the passage was complete. This kept the Prussians off balance as they dispersed their army attempting to guard all possible avenues of approach, and confused them as to the location of the French main body and its target. 
When Napoleon discovered the enemy on his left flank on the 13th he wheeled his bataillon carré to the left to bring the Prussians to battle. In a period "...of 24 hours Napoleon was in a position to concentrate 145,500 men at a decisive point; no better evidence of the excellence of the flexible coordination of the bataillon carré system is required." The retreating Prussian army was spread out and caught in a trap. Napoleon was able to concentrate overwhelming power against a portion of the Prussian army and destroy it at Jena, while one of his corps held off desperate attacks by the larger Prussian force and finally put it to flight at Auerstadt. Having forced the enemy to battle on his terms and defeated him, Napoleon now began a relentless pursuit of the remnants of the once proud Prussian army. Within 33 days he had occupied Berlin and virtually destroyed the Prussian army. "The whole war had lasted only seven weeks." 
In 1805, Napoleon advanced against the Austrians on the Danube at Ulm, with seven corps d'armée in echelon along the Rhine. His front extended over 200 kilometers, but as the corps wheeled to the right and converged on General Mack, his front shrank to 90 kilometers. The helpless Mack was caught in a trap before he had any idea as to what was occurring to him, and finally surrendered with 30,000 of his men before any major battle had been fought. The corps system had achieved an operational triumph and up to 60,000 enemy soldiers were taken prisoner during the campaign. 
The development and organization of the corps d'armée, and the doctrinal advances thus allowed, still affect our current organizations, and operational and tactical techniques. In organization, the corps of 1805 did not look much different from the corps of 1991. Operation Desert Storm, operationally, bears a striking resemblance to Napoleon's Ulm campaign. In both, the enemy's left flank was anchored on a barrier which blocked his retreat: the Persian Gulf in Desert Storm, and the Alps in the Ulm campaign. The Coalition Forces and the French both deployed their corps along an expansive front and wheeled to the right cutting off the rear of the enemy forces and severing his line of communications and retreat, while another corps attacked frontally to pin the enemy and deceive him as to the main effort. Even our current tactical techniques owe much to their Napoleonic inheritance. In armor and mechanized infantry battalions, a standard form of movement is the diamond. If you substitute the corps d'armée for armor and mechanized infantry companies, the formation is strikingly similar to le bataillon carré, and provides the same benefits to the battalion that the formation gave to Napoleon's army in 1806.
By 1805, the nature of warfare had changed dramatically from the time of Frederick the Great. Napoleonic warfare was quicker and more fluid. Two significant reasons for these changes were the organization of the corps d'armée and the use of the bataillon carré system. These changes, which occurred over 190 years ago, still have profound influence on our current organizations and doctrine.
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