Greetings Cosmic Americans!
Last time I spoke of an established United States Navy as an advantage for the Union in the Civil War. Keeping with the water theme, I thought I would turn analysis south and talk about rivers.
Rivers during the Civil War era worked effectively in two significant ways. One, as formidable barriers to attacking armies and two, as avenues of advance for attacking armies and navies. Whether or not rivers helped or hindered the Confederate cause depended on which way the attacks were being launched and which way the rivers flowed.
Not generally one for counterfactuals, it is interesting to speculate nevertheless what might have happened had Kentucky voted to secede from the Union. For one thing, the Ohio River would have been the Confederacy's northern frontier and a really neat way to keep United States forces busy figuring out how to move armies across it. But since this didn't happen, we can move on to how rivers, especially in the western theater worked against the Rebels.
United States forces had three perfectly suited avenues of advance right in to the heart of the Confederacy. The Tennessee and Cumberland Rivers more than once provided the means by which Union forces made their way south. And of course the Mississippi River (despite the Confederate defense network that lasted until 1863) worked both to bisect the Confederate states and serve as a grand highway for Union vessels. So ultimately, we will have to count the primary western river system as a disadvantage to the Confederates.
The rivers in the eastern theater had the potential to serve the Rebels well, unless of course Union forces moved inland from the coast. And this is precisely what George McClellan did in 1862. While the Potomac served as a barrier at the northern Virginia border, McClellan bypassed this and steamed inland using Virginia's eastward flowing river system. But we know what happened to him....opportunities lost, as they say. But in the event of an overland attack, eastern rivers would prove helpful for the Confederates. The Rappahannock, York, and James rivers in Virginia worked as a series of defensive lines and a real challenge for any army moving south from the Virginia northern frontier. Just ask anyone...like Union generals Burnside or Grant, for example.