What advantages did the Confederacy have, and why did its leaders think victory would be theirs?

Entering the Civil War, both the North and the South were confident of victory. What advantages did the Confederacy have, and why did its leaders think victory would be theirs? Similarly, what advantages did the Union possess entering the war? Finally, based on readings and lecture, identify at least two key causes, events, and/or decisions that allowed the North to gain the upper hand and win the war.