Both the administrations of outgoing President James Buchanan and the newly-elected President Abraham Lincoln believed that there was no legality in the secession that the eleven Southern slave states had declared. Thus, the Union--and particularly Lincoln--had a declared purpose: to reunite the United States as a single nation and preserve its territorial integrity. The previous post makes some good points: The Union held a distinct advantage in total population (approximately 23 million) compared with the seceding states (approximately nine million). The U. S. military was already established, though many of its top command defected to the Confederacy. The Union would eventually suit up more than two million men into its ranks--double that of the Confederacy. The Union held a major advantage in its naval operations, and this was perhaps it's greatest military asset. The Union artillery remained superior throughout the war, and by war's end, the Union cavalry had achieved equal status with the Confederate horsemen who had been dominant during the first three years. The sheer numbers of the Union infantry eventually overwhelmed the Southern troops, who had outfought the Federals for most of the war despite a huge numerical disadvantage.
The most important non-military advantage held by the Union was its vast natural resources and factories. Weapons manufacturers flourished in the North, while production was limited in the South. Corn grown in the Northern states became more important than King Cotton: Europe had a surplus of cotton but suffered a grain crisis during the war years. The Union threatened to declare war on any nation who recognized the official status of the Confederacy, and no nation officially came to the aid of the South. Nations were reluctant to run the Union naval blockade, which controlled both the Northern and Southern coasts. Internation public opinion against slavery also worked to the North's advantage.
The North had:
- control of the government.
- control of factories and production of goods needed to fund the war.
- had nearly 3 times the population as the South
- naval power
- military leadership
Most of which the South laacked.