 Early in the war, Union naval forces established a blockade under the command of Admiral David Farragut.The Confederates countered the blockade by constructing "blockade runners;" fast, shallow-draft, low-slung ships that could either outrun or evade the blockaders, maintaining a trickle of trade in and out of Mobile.The "CSS Hunley", the first submarine to sink an enemy vessel in combat, was built and tested in Mobile before being shipped to Charleston, South Carolina.