The very size of the Confederate states allowed many avenues for the Union army to penetrate and defeat the seceding states. President Lincoln had many choices before him with pros and cons accompanying each of them. Aside from the obvious upper Mississippi River system, the Union had the choice of going through the Gulf of Mexico coast, through Virginia’s coast, and along the Ohio and Cumberland Rivers.
The second most obvious maneuver would have been to come at the Confederacy through the Gulf of Mexico. This was open water that led to the mighty Mississippi from the Southern end and had the largest Confederacy city located there, New Orleans. This strategy was part of the Anaconda Plan that was dismissed as a whole, but the value of coming at the Confederacy from the South was seen. This plan was taken into hand in 1862 by a combined effort of the Union army and navy at New Orleans. The fall of New Orleans was a momentous success for the Union as it handed over the large city as well as control of the largest waterway in the Confederacy to the Union army and navy. The move to come at the Confederacy from the South proved successful.
The avenue of attack from the sea on the Eastern seaboard, notably Virginia, was largely overlooked largely due to lack of amicable geography for the Union navy to use. This section of the Confederacy was largely attacked via the Union army as a direct attack from the North. As part of the Anaconda plan, the Eastern seaboard would have been utilized, but the young navy made that difficult.
The Union had the option of moving South from the Ohio and Cumberland Rivers which they readily took advantage of. By taking control of Fort Donelson, the North took possession of these major waterways and moved further south taking Nashville. This avenue allowed the North to penetrate deep into the South and strike a huge blow against the Confederacy.
By putting a circle around the South, the North had an entire circumference of choices to penetrate and defeat the enemy. Each one came with its pros and cons. Most avenues were utilized, proving effective for the Union military.