“Hold the attention of your enemy with a minimum force, then quickly strike him suddenly and hard on his flank or rear with every weapon you have.” - Gen. A.A. Vandegrift
May 2013 marks the 150th anniversary of the Battle of Chancellorsville. It is one of the premiere battles that military professionals around the world study to understand the art of warfare. The chaos, courage, and suffering that took place at the Battle of Chancellorsville was so expansive and extreme that it is difficult for twenty-first century minds to grasp. Numbers vaguely tell the story of the savagery: total Confederate casualties 13,156, of whom 1683 were killed, 9277 were wounded, and 2196 were prisoners of war. Union casualties totaled 16,845 with similar proportions.
What possible lessons could still be useful today from this massacre of a battle that took place a century and a half ago? If the history of war teaches us nothing else, it is that even though equipment and tactics change the human element changes little. Consistently the ages remind us that the human element is the only thing that resembles a constant in the progression of warfare.
The fighting that unfolded midway between the Union and Confederate capitols reveals timeless principles about military planning, maneuver, surprise, deception, and initiative. Yet even more astounding than the physical actions that transpired, the battle provides profound insights into the minds of military commanders and their soldiers on both sides.
Verities such as energy, firmness, staunchness, emotional balance, and strength of character are enduring markers of successfully leaders across the millennia of human conflict. Such universal lessons are essential for officers who aspire to master the art of war. To fully understand and apply them in modern warfare requires a thorough immersion of thought into the context of a major historical campaign. Understanding the reasons why past commanders took the decisions they did is a vitally important part of a military education.
The Strategic Setting
The terrible battles of Antietam and Fredericksburg in September and December of 1862 revealed the orthodox thinking of leaders in both armies. American military leaders of this era were raised during a transformational period in human development; when mankind was adapting to the age of enlightenment and birth of the industrial revolution. Most senior Army leaders were products of the West Point education system that stressed engineering, the campaigns of Napoleon Bonaparte, and the theories of Antoine Jomini. This mental framework led to a broad-based inclination by Civil War leaders in both armies to take the offensive. Author Michael Phipps summarizes the Jomini-Napoleon ideals that permeated early U.S. Military Academy graduates.
Jomini, like Napoleon, preached the offensive. One of the most quoted passages from Art of War is, “A general who waits for the enemy like an automaton without taking any other part than that of fighting valiantly, will always succumb when he shall be well attacked.” 
The methodical warfare that was ingrained in the minds of officers was based on a few simple principles. Chief among these was the principle of maneuvering to concentrate massed forces against a weak point in the enemy’s formation. Jomini sums this up in the following statement,
The employment of forces should be regulated by two fundamental principles: the first being, to obtain by free and rapid movements the advantage of bringing the mass of the troops against fractions of the enemy; the second, to strike in the most decisive direction…
By the spring of 1863 Union and Confederate armies in the eastern theater of war were preparing to resume the bloody struggle to settle political differences. The wonton destruction of human life and war materiel that occurred at Antietam and Fredericksburg had a shocking effect on psyches and war machines. Frontal assaults across open terrain against entrenched forces had led to the slaughter and maiming of tens of thousands of Americans. These tragic battles necessitated the installation of several new leaders, most notably General Joseph Hooker as head of the Army of the Potomac (AOTP).
Concurrent with his appointment as new commanding general, General Hooker worked closely with the war department to formulate a new plan for breaking the Confederate stronghold on the Rappahannock River. Hooker’s plan was highly detailed and well designed, yet simple in concept. It sought to take full advantage of Union strengths in manpower and logistics. The thoroughness of the plan and its perceived decisive advantages, instilled widespread confidence in the minds of AOTP officers. The result was that when Hooker started moving forces, the AOTP was “all in” on a predetermined course of action. Said differently, they had mentally put all their eggs in one basket.
In early 1863 the AOTP was in Falmouth, Virginia, and the Confederate Army of Northern Virginia (ANV), under General Robert E. Lee, was in Fredericksburg, Virginia. Hooker had a two-to-one advantage in manpower over Lee and his plan was designed to take full advantage of this inequality. Hooker planned to divide his army. One part would remain near Fredericksburg under the command of General John Sedgwick, while a larger force under Hooker would cross the Rappahannock River upstream and attack the ANV from the west.
Railroads were vital supply lines and thus critical vulnerabilities that each side attempted to seize or disrupt. The Union plan was based, in part, on this fact. With the Army of Northern Virginia (ANV) dug in around Fredericksburg, Hooker planned to send 10,000 cavalrymen, led by General George Stoneman, on a deep raid toward Hanover Junction, while he took the central axis through Chancellorsville and Sedgewick boxed in the Confederates from the east. The Union plan assumed that once Lee realized his lines of communication with Richmond were at risk, the ANV would have only two courses of action: conduct a two-front battle around Fredericksburg or withdraw to the south.
The Union Plan Meets Reality
“Since all information and assumptions are open to doubt, and with chance at work everywhere, the commander continually finds that things are not as he expected.” “[N]ew information and reevaluation are not enough to make us give up our intentions; they only call them in question. We now know more, but this makes us more, not less uncertain.” - Clausewitz
Hooker’s expectations skewed his view of reality on several occasions. First, he convinced himself that Lee had but two courses of action so he looked for indications that Lee was reacting in accordance with one of these two choices. His plans did not anticipate that Lee would—contrary to military doctrine—initially divide his forces. Thus, when a rear guard force of five brigades under General Early was left near Fredericksburg, Sedgewick and Hooker believed that, per the plan’s script—and some creative ANV deception—the Confederate force at Fredericksburg was stronger than they actually were. This ambiguity, coupled with miscommunication between the commanding general and Sedgwick, caused critical delays in the AOTP pincher thrust from the east.
Another factor that altered Hooker’s plan at the outset was that Stoneman’s cavalry was severely delayed in their assignment to disrupt Lee’s southern supply and communication lines. An integral part of Hooker’s plan was his preference to fight on the tactical defensive, as opposed to the revisiting the AOTP’s offensive tragedies in recent battles. Hooker’s desire to wait for an assault by the ANV proved to be the tipping point in the AOTP plan because it ceded the initiative to Lee.
Hooker again deceived himself on May 1st when he encountered ANV forces east of Chancellorsville. This development suggested that Lee had decided to take the tactical offensive which, as Antietam and Fredericksburg proved, could be a very costly decision. At the same time, Hooker’s belief that much of Lee’s army was still at Fredericksburg did not fit into his plan. Lee appeared stronger in two places than he should have been (and actually was). This confusion, coupled with confounding demonstrations by Lee on May 2nd, caused Hooker to remain inactive as the threat grew that morning. Hooker’s plan ran into trouble because it had become dogma and its unquestioned structure no longer matched reality.
This leads us to an important observation; that leaders must be agile minded and able to adapt to circumstances. In the words of S.L.A. Marshall,
The test of fitness to command is the ability to think clearly in the face of contingency or opportunity. Improvisation is of the essence of initiative in all combat just as initiative is the outward showing of the power of decision. 
Foreordained beliefs again clouded Union thinking when on the morning of May 2nd, General Stonewall Jackson’s Corps began its famous flanking march. Despite the fact Jackson was seen moving southwest past Catharine’s Furnace, little action was taken to adjust the Union plan. Union commanders believed, as the plan had predicted, that Lee had opted to withdraw to the south. However, Hooker was also aware of the possibility that Jackson might be undertaking a flanking maneuver. He took three actions; he sent a message to Maj. Gen. Oliver O. Howard: “We have good reason to suppose the enemy is moving to our right. Please advance your pickets for purposes of observation as far as may be safe in order to obtain timely information of their approach.” Hooker's second action was to send orders to Sedgwick to attack at Fredericksburg if “an opportunity presents itself with a reasonable expectation of success.” Finally, Hooker ordered General Daniel Sickles, commander of the III Corps (at the center of the Union line) to “advance cautiously toward the road followed by [Jackson], and harass the movement as much as possible.” Sickles sent an elite regiment of U.S. Sharpshooters to reconnoiter Jackson’s column. The sharpshooters caught up with the tail of Jackson’s column and mauled and captured part of the rear guard regiment. Despite the fact that many of the prisoners told their captors that Jackson would pay them back later in the day, rigid minded, plan-oriented AOTP leaders discounted this fact and no follow-on action was taken.
The preconceived notion that the enemy would react in accordance with the plan undercut the AOTP’s ability to take aggressive action outside the boundaries of the plan. This was the milieu of false confidence that was in the minds of Union leaders when Jackson struck Howard’s Corps from the West. While the physical damage that Jackson caused was significant, the psychological damage delivered was devastating. The Confederates ultimately won at Chancellorsville and drove Hooker back toward the Rappahannock. They then turned to face Sedgwick’s eastern command at Salem Church on May 3-4, 1863. Sedgwick fended off Confederate attacks from three directions, but finding himself almost encircled, he also retired to the river. At that point, Hooker ended the Chancellorsville campaign and crossed the Rappahannock, leaving the field in the possession of an army half the size of his own.
The Confederate Perspective
“In order to win, we should operate at a faster tempo or rhythm than our adversaries--or, better yet, get inside [the] adversary's Observation-Orientation-Decision-Action time cycle or loop. ... Such activity will make us appear ambiguous (unpredictable) thereby generate confusion and disorder among our adversaries--since our adversaries will be unable to generate mental images or pictures that agree with the menacing as well as faster transient rhythm or patterns they are competing against.” – Col John Boyd
General Lee was in a much different predicament and possessed a different mental temperament than Hooker. Obliged to assume the strategic defensive, and lacking much of Longstreet’s Corps, due to operations south of Richmond, Lee was severely outnumbered and hemmed in from three sides. Such a predicament, in fact, played into Lee’s strong suit as a commander. Lee was bold and decisive and always sought ways to disadvantage his enemy through unexpected actions. He understood that owning the initiative can make up for inferior numbers; and that initiative opens opportunities for its owner and forecloses them to one’s opponents. As Clausewitz says, “The more boldness lends wings to the mind and the discernment, so much the farther they will reach in their flight, so much the more comprehensive will be the view, the more exact the result, but certainly always only in the sense that with greater objects greater dangers are connected.” Squeezed into a tight situation at Chancellorsville, Lee’s confidence in himself and his forces, especially Jackson, combined with an understanding of Hooker’s tendencies, enabled him to take bold, rapid action against Hooker’s plans. His actions against AOTP maneuvers were in keeping with one of Sun Tzu’s famous maxims on war, “What is of supreme importance in war is to attack the enemy’s strategy.”
Lee used initiative to disrupt enemy plans and create more favorable conditions. Again from Clausewitz, “Loss of moral equilibrium must not be underestimated merely because it has no absolute value and does not always show up in the final balance. It can attain such massive proportions that it overpowers everything by its irresistible force.” In doing so, he sought to create confusion for the enemy, while harnessing the cohesion of highly-disciplined veteran forces. Military theorist J.F.C. Fuller makes clear the significance that psychological effects can have on the battlefield.
The enemy does not attack him physically, but mentally; for the enemy attacks his ideas, his reason, his plan. The physical pressure directed against his men reacts on him through compelling him to change his plan, and changes in his plan react on his men by creating a mental confusion which weakens their morale. Psychologically, the battle is opened by a physical blow which unbalances the commander's mind, which in its turn throws out of adjustment the moral of his men, and leads to their fears impeding the flow of his will. If the blow is a totally unexpected one, the will of the commander may cease altogether to flow, and, the balance in the moral sphere of war being utterly upset, self-preservation fusing with self-assertion results in panic.
One upside to the ANV’s small numbers was that it was lighter and more maneuverable than the AOTP. Lee used this advantage, along with his interior lines, to move his forces into a more favorable position. This is consistent with modern warfare doctrine. Marine Corps doctrine says that maneuver warfare is a philosophy that seeks to “shatter the enemy’s cohesion through a variety of rapid-focused and unexpected actions which create a turbulent and rapidly deteriorating situation with which the enemy cannot cope.”
To act inside the decision cycle of the Union army and exploit the benefits of initiative and maneuver warfare, Lee used a trust-based command and control philosophy that was highly decentralized. This method is still in use by U.S. forces today. Marine Corps doctrine purports that,
Mission command and control offers the flexibility to deal with rapidly changing situations and to exploit fleeting windows of opportunity. It provides for the degree of cooperation necessary to achieve harmony of effort yet gives commanders at all levels the latitude to act with initiative and boldness.
Relevant Lessons for Today
Chancellorsville offers an almost unlimited number of valuable lessons for the modern military professional. The most important of these include:
- The importance of initiative. The importance of initiative cannot be overstated. Initiative is more than executing offensive actions within the physical domain. It also has significant advantages within the moral and cognitive domains. It yields broad advantages to individuals that possess it and organizations that exploit it. Ultimately, initiative engenders freedom of action within physical and non-physical realms and empowers one to anticipate, if not dictate changing conditions. Hooker had control of the situation as long as he kept moving, and kept following his plan. When he halted and Sedgwick did not advance, Lee seized the initiative and controlled events for the rest of the campaign.
- Mental agility and adaptability. Hooker was married to a plan, Lee wasn’t. In the chaos of combat, commanders must remain open to improvise and adjust as circumstances change. Hooker’s assumption that Lee had only two courses of action was the greater of two fatal mistakes in the campaign. This erroneous assumption in his plan led to Hooker’s decision to stop and hold in place at Chancellorsville, which was the other mistake. In short, neither Hooker’s plan nor his mentality allowed for the play of chance. On the other hand, Lee’s mentality and the temperament of his forces were much more agile and flexible. Infused with confidence, the ANV executed through a sense of trust. Trust facilitates rapid decisions and right actions. It is the assurance another will act in good faith to achieve a goal. Trust is the coin of decentralize command and control. Forces that possess trust have a distinct advantage in high-speed warfare.
- The principles of war. Current reverence for universal truths of warfare can be traced back to Jomini, who said “there have existed in all times fundamental principles… unchanging, independent of the kinds of weapons, of historical time and of place.” For better and for worse, Lee and Hooker anchored their planning and decisions on time-tested principles, many of which are reflected in contemporary U.S. doctrine.
- Mass - Concentrate combat power at the decisive place and time.
- Objective - Direct every military operation towards a clearly defined, decisive, and attainable objective.
- Offensive - Seize, retain, and exploit the initiative.
- Surprise - Strike the enemy at a time, at a place, or in a manner for which he is unprepared.
- Economy of force - Allocate minimum essential combat power to secondary efforts.
- Maneuver - Place the enemy in a position of disadvantage through the flexible application of combat power.
- Unity of command - For every objective, ensure unity of effort under one responsible commander.
- Security - Never permit the enemy to acquire an unexpected advantage.
- Simplicity - Prepare clear, uncomplicated plans and clear, concise orders to ensure thorough understanding.
Lee’s use of divided forces and Jackson’s flank march were consistent with six of the nine principles of war: Initiative, Offensive, Maneuver, Mass, Economy of Force and Surprise. However, Lee also knew when to deviate from conventional wisdom when he split his “mass” into three smaller groups. This shows that the principles of war are useful in framing military plans, but not absolute laws that must be obeyed. Hooker also used Initiative, Offensive, Maneuver, Mass, Economy of Force, along with Simplicity, in his initial plan to trap Lee. But, when he halted his advance, he gave up the benefits of the offensive and maneuver.
To succeed in future conflicts where information is exchanged around the globe instantaneously requires leaders that are competent in chaos and can make decisions rapidly with confidence. Leaders must understand the importance of holding the initiative. They must remain mentally agile and adaptable. They must know and apply, but not become slaves to the principles of war. Speed of decision is essential to gaining and maintaining the initiative. Initiative enables the force that holds it to dictate the context of battle on terms it deems most favorable to itself and its ends. By generating a higher operational tempo through superior decision speeds, an inferior force can wrest the initiative from an otherwise dominant adversary and dictate the terms of engagement. Owning initiative can also disrupt enemy cohesion and morale. Decentralized decision making at the tactical edge is inherently faster and more dexterous than that of remote centralized decision authorities, especially in geographically dispersed, complex environments. Decentralized execution enables speed, surprise, and decisiveness. So as we commemorate the series of battles that took place 150 years ago, and the painful sacrifices that so many on each side experienced, it is also important to understand, preserve, and apply forward the enduring lessons of war.
. General A.A. Vandegrift, USMC, Battle Doctrine for Frontline Leaders, 1944, Reprinted by Marine Corps Education Center, 1981
. Douglas Freeman, Robert E. Lee, Vol III, Ch 1, p.5, November 1, 1977, Published by Charles Scribner’s Sons, New York and London, 1934
. Carl Von Clausewitz, On War, p.104, Produced by Charles Keller and David Widger, February 2006; Updated January 2013; Translated by Colonel J.J. Graham, 1874; London Reprinting 1909
. Michael Phipps, Mahan at West Point, “Gallic Bias,” and the “Old Army”: The Subconscious of Leadership at Gettysburg, November 2011
. A.H. Jomini, Summary of the Art of War, p. 328, Military Service Publishing Co., Harrisburg, PA, J.D. Hittle, 1958
. Clausewitz, On War
. S.L.A. Marshall, Colonel, AUS, Men Against Fire; the Problem of Battle Command in Future War, Originally Published: Washington: Infrantry Journal; New York: William Morrow and Company, 1947
. John Boyd, Patterns of Conflict, Produced by Ginger Richards, 2007; Original Version December 1986
. Clausewitz, On War
. Sun Tzu, The Art of War, Published c 610 BC, Translated by Samuel B. Griffith, October 2005
. Carl Von Clausewitz, On War, p.104
. J.F.C. Fuller, Colonel, D.S.O., The Foundations of Science of War, pp 126-127, London: Hutchinson & Co. (Publishers), LTD., Paternoster Row, E.G., Army General Command and Staff Press, Reprinted 1993
. Marine Corps Doctrinal Publication (MCDP) 1, Warfighting, 20 June 1997
. US Marine Corps Doctrinal Publication 6, Command and Control, 4 October 1996
. A.H. Jomini, Summary of the Art of War
. U.S. Joint Doctrine, Joint Publication 3-0, Joint Operations, 11 August 2011