As is my wont, I will sometimes browse the pages of Wikipedia to see just how uneven the site is. The entry for Confederate General Earl Van Dorn did not disappoint:
He is considered one of the greatest cavalry commanders to have ever lived.
That's a remarkably bold statement for a someone whose resume was far from exemplary and whose career was so brief.
His entry exemplifies what I think is the unwarranted praise heaped on Confederate cavalry leaders, especially those known for raiding behind enemy lines. I'm thinking in particular of Nathan Bedford Forrest and John Singleton Mosby.
Both men combined rapid movement, ferocious attacks with dauntless personal courage and their exploits are quite impressive.
However, there are some important caveats. The first is that they were leading veteran first-line troops against rear-area security forces, rarely facing first-rate troops or leaders. It was common practice in the Civil War to send troops forward without completing their training, the assumption being that it would be finished while in a quiet garrison post. The Union also utilized short-term enlistees in these positions, troops whose length of service might be a short as 90s days. They were therefore little more than armed civilians.
These troops were almost invariably infantry, meaning they were at a considerable disadvantage vs hit-and-run attacks.
The Confederates were also generally operating on interior lines, which meant the not only knew the terrain, they knew the people, who provided them with excellent intelligence. Union troops, by contrast, were often isolated and had little knowledge of what was going on around them.
About the only advantage Union forces regularly had was numbers, which is of little use in countering hit-and-run tactics.
All of which is to say that the raiders' success was to be expected.
While it raised Confederate morale, and created iconic heroes, I think it was ultimately harmful to the Rebel cause. There are two reasons for this.
The first is that capable Union commanders soon learned that they could have either secure lines of supply or freedom of maneuver, but not both. Their solution was to pack their troops with ammunition and rely on foraging to feed them. Ulysses S. Grant tested this method in his Big Black River campaign, and his lieutenant, William T. Sherman, further refined it during the subsequent Meridian campaign.
The culmination of this was Sherman's March to the Sea and subsequent march through the Carolinas.
This brings us to the second unintended consequence: the devastation wrought be these forces. Throughout history armies have foraged to sustain themselves. While we think of them as looting and pillaging, this was not always the case. Julius Caesar famously sent emissaries ahead of his troops to purchase supplies and thereby gain allies. Of course, those who weren't willing to make a deal usually ended up getting plundered, but the point is that Union forces could have done the same had the local populace been open to it.
In the event, the standard practice was to take what could be carried and destroy what was left. This inflicted great hardship on Confederate civilians, creating a refugee crisis throughout the South.
In the case of the Shenandoah Valley, the destruction was necessary because the prevalence of raiders and the asymmetrical terrain made it impossible for Union garrisons to sustain themselves.
Thus, while the raiders did inconvenience Union forces and arguably slowed the advance of Union forces, they also ensured that when they did advance, they would wreak untold destruction on the very people the raiders were trying to protect.
Throughout history, we have seen situations where a specific tactic is initially successful, but the counter proves more dangerous than what was happening before.
I will also add that claims to world-historical status for minor figures like Van Dorn are particularly ludicrous when compared to the vastly larger scope of Chinese military history.