Hi! So...Armies are big. They have thousands of soldiers and require absolutely enormous and constant influxes of reinforcements, food, medical supplies, weapons, ammunition, news, order and other essentials. Armies can't bring enough of that with them to maintain themselves so they traditionally rely on either forage (i.e. robbing the locals) or supply lines.

Hilton Head Island is between Charleston and Savannah. An invasion would have required the union to send hundreds of thousands of troops around Tennessee, land them on Hilton Head and then keep up a constant stream of reinforcements behind the lines, past the coast of Tennessee.

Logistics are DIFFICULT, especially ore-internal combustion engine and Armies tend to move along waterways and roads. A breakout was extremely unlikely.

Much more likely is that any significant troop concentration would be cut off, surrounded and forced to surrender.

The US civil war was a political conflict. Losing 10, 50 or 100 thousand soldiers for no good might have swung the war the other way.

Hey there,

Just to let you know, your question is fine, and we're letting it stand. However, you should be aware that questions framed as 'Why didn't X do Y' relatively often don't get an answer that meets our standards (in our experience as moderators). There are a few reasons for this. Firstly, it often can be difficult to prove the counterfactual: historians know much more about what happened than what might have happened. Secondly, 'why didn't X do Y' questions are sometimes phrased in an ahistorical way. It's worth remembering that people in the past couldn't see into the future, and they generally didn't have all the information we now have about their situations; things that look obvious now didn't necessarily look that way at the time.

If you end up not getting a response after a day or two, consider asking a new question focusing instead on why what happened did happen (rather than why what didn't happen didn't happen) - this kind of question is more likely to get a response in our experience. Hope this helps!