Confederate Strategy:
Jefferson Davis agreed; early in the war he seems to have envisaged a strategy like that of George Washington in the Revolution. Washington traded space for time; he retreated when necessary in the face of a stronger enemy; he counterattacked against isolated British outposts or detachments when such an attack promised success; above all, he tried to avoid full-scale baffles that would have risked annihilation of his army and defeat of his cause. This has been called a strategy of attrition--a strategy of winning by not losing, of wearing out a better equipped foe and compelling him to give up by prolonging the war and making it too costly.
But two main factors prevented Davis from carrying out such a strategy except in a limited, sporadic fashion. Both factors stemmed from political as well as military realities. The first was a demand by governors, congressmen, and the public for troops to defend every portion of the Confederacy from penetration by "Lincolns abolition hordes." Thus in 1861, small armies were dispersed around the Confederate perimeter along the Arkansas-Missouri border, at several points on the Gulf and Atlantic coasts, along the Tennessee-Kentucky border, and in the Shenandoah Valley and western Virginia as well as at Manassas. Historians have criticized this "cordon defense" for dispersing manpower so thinly that Union forces were certain to break through somewhere, as they did at several points in 1862.
The second factor inhibiting a Washingtonian strategy of attrition was the temperament of the southern people. Believing that they could whip any number of Yankees, many southerners scorned the notion of "sitting down and waiting" for the Federals to attack. "The idea of waiting for blows, instead of inflicting them, is altogether unsuited to the genius of our people," declared the Richmond Examiner. "The aggressive policy is the truly defensive one. A column pushed forward into Ohio or Pennsylvania is worth more to us, as a defensive measure, than a whole tier of seacoast batteries from Norfolk to the Rio Grande. The southern press clamored for an advance against Washington in the same tone that northern newspapers cried On to Richmond. Beauregard devised bold plans for an offensive against McDowell. But the question became moot when Beauregard learned of McDowell's offensive against him.
The Confederates eventually synthesized these various stands of strategic theory and political reality into what Davis called an "offensive-defensive" strategy. This consisted of defending the Confederate homeland by using interior lines of communication (a Jominian but also common-sense concept) to concentrate dispersed forces against an invading army and, if opportunity offered, to go over to the offensive, even to the extent of invading the North. No one ever defined this strategy in a systematic, comprehensive fashion. Rather, it emerged from a series of major campaigns in the Virginia-Maryland and Tennessee-Kentucky theaters during 1862, and culminated at Gettysburg in 1863. It almost emerged, in embryonic form, from the first battle of Manassas (Bull Run) in July 1861, a small battle by later Civil War standards but one that would have important psychological consequences in both the North and the South.
Source: "Battle Cry of Freedom" by James M. McPherson.
Union Strategy:
It is not easy to reconstitute the general air of confusion and uncertainty in which the initial Union strategy took shape. There was a sharp division in the Cabinet and in the army as well over the appropriate strategy to pursue in attempting to subdue the South.
The strategy that Lincoln became determined to pursue was aggressive penetration of the South. The inevitable next question was how was that strategy to be best effected. One needs, first of all, to have reference to the map of the South which constitutes the endpapers of this volume. There it is seen that the South had two major lines of vulnerability: several thousand miles of virtually undefended seacoast running from Norfolk, Virginia, around the tip of Florida and along the Gulf of Mexico to New Orleans and, in the West, almost a thousand miles of the Mississippi River, stretching from St. Louis to New Orleans, which constituted a line of access into the Deep South and, for the Southerners, an obstacle separating them from their trans-Mississippi allies--Texas, Arkansas, and Missouri. Moreover, the Ohio River entered the Mississippi at Cairo, Illinois, and fifty miles to the east of that conjunction, the Cumberland and Tennessee rivers emptied into the Ohio, coming from a southeasterly direction parallel to each other and roughly parallel to the Mississippi. The South had to defend that river network at all costs. In the hands of the North it would leave the South vulnerable to invasion from a hundred points.
New Orleans was the hinge of the lower South--the point where the coastline joined the great arterial waterway of the Mississippi. The Northern strategy was thus, like all proper strategies, dictated in large part by the terrain. Plans were made immediately for three amphibious operations, two combined land-sea operations, directed at vulnerable points on the North and South Carolina coast--one at Roanoke Island, the other at Port Royal, just south of Charleston; the other expedition was directed at New Orleans itself.
Meanwhile, the Army of the Potomac, with McClellan in command, was organized with the mission of capturing Richmond. As the months passed, a series of additional armies were formed along the line of the Ohio and upper Mississippi--the armies of the Ohio, the Cumberland, the Frontier, Kansas, the Mississippi, the Mountain, the Southwest, the Tennessee, the West Tennessee, and, near the end of the war, the Shenandoah, finally fifteen in all (the Confederacy formed twenty-four "armies"). The real story of the war--the battles and campaigns that finally brought it to its bloody conclusion--took place far away from Washington and Richmond, at Shiloh, Tennessee, Vicksburg, Mississippi, Chickamauga, Georgia, and in a dozen other such engagements. But the facts that the capitals of the North and South were so close together, little more than a hundred miles apart, and that the Confederate capital was, moreover, in the extreme northeastern corner of the geographical area covered by the Confederacy produced a strange distortion, first in the war itself and then in our comprehension of it. The grand strategy developed by Lincoln, his Cabinet, and General Winfield Scott and the actual deployment of Union armies certainly took account of the points of Southern vulnerability, but the focus of public attention remained fixed on the two armies that confronted each other in Virginia--the Army of the Potomac and the Army of Northern Virginia.
Source: "Trial By Fire, A People's History of the Civil War and Reconstruction" by Page Smith, Volume 5, Chapter 4, Pages 97,98, and 99.