Final answer:
Forts Henry and Donelson protected the Tennessee and Cumberland rivers, which were important to the South for transportation and communication purposes.
Step-by-step explanation:
Forts Henry and Donelson protected the Tennessee and Cumberland rivers. These rivers were important to the South because they provided key transportation routes for moving supplies and troops. Controlling these rivers was crucial for the Confederacy to maintain communication and supply lines between the western and eastern parts of their territory.