The Military Level
First, The South had some notable advantages, including what are called “interior lines.” Defending its own territory from an external threat, it had shorter “lines of communication,” had greater familiarity with the terrain, and could count on the support of the local population.
However, the North had many more advantages. The battle force ratios favored the North, generally outnumbering the South in every battle except Chickamauga (September 1863). The North had the larger population base from which to draw recruits.
Second, after the Emancipation Proclamation took effect in January 1863, the North enlisted and employed blacks, the South did not. About 180,000 blacks served in the Union Army; 37,000 were killed and killed at a rate 40% higher than whites. Twenty-one distinguished themselves and won the nation’s highest military honor, the Medal of Honor.
Third, the competence of the North’s military leaders eventually equaled the South’s. At the outset of the war, the South clearly had the advantage of superior leaders in men like Robert E. Lee, Stonewall Jackson, James Longstreet. However, as the war continued, the North’s officer corps developed and improved in competence. Also, Lincoln eventually found the right generals who could prosecute the war to win battle victories: Ulysses S. Grant, William T. Sherman, and Philip Sheridan. General Grant became commander of all Union forces in the West in October 1863, and General-in Chief of the Army in March 1864
Fourth, the South’s tactics could be quite reckless at times. Grady McWhiney and Perry Jamieson contend:
“that the Confederates bled themselves nearly to death in the first three years of the war by making costly attacks more often than did the Federals. Offensive tactics, which had been used so successfully by Americans in the Mexican War, were much less effective in the 1860s because an improved weapon—the rifle—had vastly increased the strength of defenders. … The Confederates favored offensive warfare because the Celtic charge was an integral part of their heritage.” (Attack and Die, p. xv)
New technology had given the advantage to the defense rather than the offense. In the 1840s the French had developed the minié ball. This, with the rifle (not musket), meant that the killing zone increased from 50 yards to 150 or more yards. The South aggressive offensive tactics often proved costly, and especially as manpower ran short, they simply could not afford the losses that such tactics brought.
The final, crucial dimension which always matters in war is political will: the determination and resolve of a political actor to continue to prosecute a war.
In the early stages of the war, because of the Southern victories and the indecisiveness of the Northern generals, such as George McClellan, the South had swagger and confidence. But this changed as the war progressed.
Southerners quite early lost their desire to volunteer, forcing the South to implement its First Conscription Act in April 1862. The early elation of Southerners evolved into dogged determination. Militarily, the summer of 1863 was a turning point. In the largest land battle in the history of North America, the South led by Robert E. Lee, invincible to that point, was soundly defeated at Gettysburg by the North. Vicksburg, the final Southern bastion on the Mississippi River, fell shortly afterward.
As the war persisted, the Confederacy could not hold together under the strain of war as well as the North. By 1865 the South seemed to be full of wounded men, and women and children who were war refugees. Its will simply crumbled faster than the North’s.
After the victories at Gettysburg and Vicksburg, the North’s will and determination continued to grow. In early 1864 Grant so impressed Lincoln with his victories in the West that Lincoln brought him east and made him commander of all Union forces. Lincoln’s own determination was reinforced now after finally finding the right commander. His will and the will of the North were decisively reinforced with the fall of Atlanta in September 1864, and Lincoln’s subsequent re-election in November.
Conclusion: Not only in the military sphere, but in the political, economic, and social spheres, the North possessed at the outset, or gained as the war progressed, a number of distinct advantages over the South. These advantages, coupled with its better decision making in these spheres, eventually caused the South’s will to falter faster than the North’s and for peace to break out in the spring of 1865.