The lack of ability to raise taxes to operate the national government, and the requirement for a unaimous vote of the state's to pass legislation. The federal government had no way to force the states to obtain the funds it needed to operate. State only sent funds it needed to operate.
One. The Battle of Antietam.
The reason I say one is because the Confederacy has better War Generals, they had a more experienced militia. That’s why they were undefeated for so long. But The battle of Antietam of 1862 was the battle the Union, the North, celebrated because of their first victory against the Confederacy, the South.
They're "carpetbaggers," which was named after the cheap bags they usually carried.