Five reasons why the Union won

The American Civil War was perhaps the single, most pivotal period in our nation's history. There was a lot at stake: from slavery to individual sovereignty to the Republic itself.
Although I've come to understand and even appreciate the Confederate point of view, I truly believe that the Union's preservation was Divine Providence.
The Union was victorious because God wanted to preserve it for His glory. He had bigger, grander and more divine plans for the United States of America, requiring her to remain "One Nation Under God" instead of several.
I've determined that the Union's triumph was nothing short of God's Will. And below I've given five reasons why I think the Union was poised for victory.

1. Bigger was better.
This is not always the case, of course, and the South very nearly proved this axiom wrong. The American Colonies certainly debunked that assumption by defeating the mightiest army in the world and winning their independence from the world's most powerful empire 80 years earlier.
But, in the end, the North was bigger and stronger. In a war of attrition, the weaker foe usually succumbs first. The armies of the United States were routinely bigger by a sizable margin than their Confederate counterparts in either theater of the war. The Union's Army of the Potomac quite often outnumbered the Army of Northern Virginia by a 2:1 and sometimes 3:1 ratio. In a shortened war, the odds were fairly even, because the Confederates made up in spirit and heart what they may have lacked in numbers.
But the longer the war dragged on, the less likely the South was to outlast the North. What started to be a war of ideas eventually became a war of attrition that the Confederacy was not equipped to win.

2. He who had the most toys won.
Not only was the Confederacy grossly out-manned and outnumbered, but it was vastly out-supplied, too. Where the North was becoming an industrial giant, the South remained agrarian.
Factories up North churned out goods that kept the Union Army well supplied and stocked. This became crucial once Gen. Grant took over command of the Army of the Potomac.
At Petersburg, he simply waited out the remainder of the war. He did to Lee what he had done to Vicksburg in 1863: He laid siege to it and waited for the enemy to surrender from attrition.
The Union could afford to do this because of the vast wealth of industry it had access to in the North.
The South, on the other hand, had virtually no industry apart from agriculture, so it could ill afford a single defeat after Gettysburg.
In fact, by late 1864, during Grant's siege of Petersburg, the Confederate ranks were shrinking swiftly due to starvation. Union Gen. Phillip Sheridan had cut off the Confederacy's bread basket in the Shenandoah Valley of Virginia; a Union naval blockade had been in place since the beginning of the war, bottling up every major Confederate port and preventing large amounts of imported goods from getting into Confederate hands; and the Union seized control of the Mississippi River after the fall of Vicksburg, effectively cutting the Confederacy off from supplies in the West.
Moreover, the South could not afford to even keep its soldiers properly shod, much less clothed. A great many Confederate foot soldiers marched without shoes, a microcosm of a greater supply shortage problem.

3. Double trouble.
Many Civil War historians will agree that Gettysburg proved to be the pivotal engagement of the war. Leading up to that battle, the Army of Northern Virginia had been bolstered by routes of the Union at Fredericksburg the previous winter and Chancellorsville that spring. Gen. Lee inspired substantial confidence in the Confederate army and he led them on an ambitious northern advance into Union territory. Had things gone differently for Robert E. Lee and the Army of Northern Virginia at Gettysburg, there's no telling how much longer the war would have lasted and if we would still be a divided country today.
As it is, the Confederates lost the Battle of Gettysburg, handing the Union a much needed shot in the arm, both for morale of the troops and support from the American public.
But while Gettysburg was arguably the fulcrum point of the war, the fact that a Union victory there coincided with a victory at Vicksburg in the West at exactly the same time made the Confederate losses all the more significant.
Not only had the Confederate army shown its own mortality at Gettysburg, but with the fall of Vicksburg came the loss of the Mississippi River as a means for transporting supplies from Texas to the rest of the Confederacy, which suddenly found itself cut off.
Vicksburg proved to be the South's undoing much more so than Gettysburg, because its loss meant a loss of supplies, putting the Confederacy at an even greater disadvantage in a war of attrition.
So, Gettysburg and Vicksburg were double blows to the Confederacy, and also double victories for the Union. After July 1863, the South became twice as weak as it had been before, and the North twice as strong.

4. Grant.
Up until Gettysburg, Union victories in the eastern theater were sparse to none. While in the West, the Union army under the command of Gen. Ulysses S. Grant had already notched significant victories at Fort Donelson and Shiloh. Then came Vicksburg at the same time as Gettysburg.
Behind virtually every major Union victory was the man affectionately called Sam Grant. He was the reason that the Army of the Potomac kept on fighting in the east, in spite of itself.
If not for the victories in the West, the Union's morale would have plunged to such depths that a cease fire may have been imminent simply because the North's heart was no longer in the fight.
But Grant kept the North going.
And he not only kept it going after assuming command of the Army of the Potomac in 1864, but he also gave it ultimate victory.
Lieutenant General Grant, as general-in-chief of the entire Union Army, along with Lt. Gen. William Tecumseh Sherman, Grant's subordinate and commander of the Union Army of Tennessee, formed a vice that squeezed the Confederacy to death.
Upon the subjugation of the Mississippi River in 1863, Union forces were able to move gradually inland and east through Tennessee. By Christmas of 1864, Sherman had marched, burned and sacked his way through Atlanta, Georgia, and to the edge of the continent at Savannah.
His (in)famous "march to the sea" successfully cut the Confederacy further in half. (This had first been done a year earlier with the fall of Vicksburg, which cut Texas off from the rest of the South.)
Sherman was then able to march northward, chasing the forces of Gen. Joseph E. Johnston, in an effort to link up with Grant in Virginia and squeeze the Confederate Army into submission.
For his part, Confederate Lt. Gen. Robert E. Lee had gotten used to the soft commanders of the Army of the Potomac. He could always count on them running with their tails between their legs when he'd out-foxed them. Time and again, Lee outsmarted his counterparts in blue.
But everything changed once Grant took command in the East.
Suddenly, the Union wasn't running away to lick its wounds as it had before. Instead, it continued to press and pursue Lee like a hungry predator, wearing down its prey until it was too tired to run anymore.
And that's exactly what happened after the siege at Petersburg. The Army of Northern Virginia had simply run out of steam. It was out of fuel and unable to run anymore.
Grant didn't outsmart Lee as his predecessors had tried to do; he simply outlasted him.

5. The moral edge.
Even a Southern-sympathizing historian like myself must admit that when it came to moral superiority, the South dropped the ball big time. It unwisely chose to base its states' rights argument on the morally depraved institution of slavery. The South was right to insist on states' rights (i.e., namely individual property rights) as guaranteed by the United States Constitution and to stand against efforts to deny those rights to Southerners. But it was wrong to defend slavery, not only because it made the South's arguments for freedom lack credibility, but also because slavery represented the very antithesis of liberty itself. To propagate slavery was to violate the very premise agreed upon by America's founders: The self-evident truth that God created all men equal to pursue life, liberty and happiness.
If the Confederacy hadn't been controlled and ultimately run by the plantation aristocracy, but rather by common Southern Americans, then it might have had a real chance of succeeding.
But the ugly reality is that slavery held the South back in the moral, social and economic dark ages. It prevented the Confederacy from diversifying and expanding its industries, all because of a few wealthy plantation aristocrats who owned or controlled the vast majority of lands in the South. And they weren't giving up their lands for progress; no way, no how.
Consequently, the South's stubborn hold on slavery was its ultimate undoing. Maintaining slave labor prevented the Confederacy from being able to compete with the North in manufacturing and production by discouraging the diversification of industries. But most of all, slavery ended up vilifying the South for generations afterward as it found itself on the losing end of a moral battle of wills.