The South did have at least two important advantages in their favor that made a Union victory far from certain in 1861. Perhaps the most important was the fact that they had better military leaders. Most of the best military officers in the United States military prior to the outbreak of the Civil War were from the South. When the Southern sates succeeded, most of these officers such as General Stonewall Jackson and General Robert E. Lee resigned their commissions and accepted positions in the Confederate Army. The Union still had some good officers, but not as many as the Confederacy and poor leadership was one of the primary causes of early Union defeats.
The South also had something of a "home field" advantage. Since the North was invading the South, the Southerners had to fight close to home. Often, they were much more familiar with the terrain than were the Northerners and they were always more desperate to win. When you believe that you are defending your wife and children from invaders, you care more about your cause than those who are simply being paid a wage to go fight for a cause that does not influence their lives as directly. This made a significant difference on the battlefield.
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