Final answer:
The first true submarine attack targeted the USS Housatonic during the American Civil War, conducted by the Confederate submarine H. L. Hunley.
Step-by-step explanation:
The first true submarine attack in warfare occurred during the American Civil War against the Union ship USS Housatonic. On February 17, 1864, the H. L. Hunley (often erroneously referred to as USS Hunley), a Confederate submarine, successfully attacked the Housatonic off the coast of Charleston, South Carolina. The Hunley used a spar torpedo mounted on a pole to inflict fatal damage to the Union ship, which led to the sinking of the Housatonic. Unfortunately, the submarine itself also sank shortly after the attack, resulting in the loss of its crew.