In what wars were submarines used in?

David Bushnell's submarine Turtle is considered the first submarine used in combat (Revolutionary War), though it never successfully attacked any vessels. It was sunk by the British while attached to its tender.

The first successful use of a submarine in warfare was in the U.S. Civil War on February 17, 1864, when the Confederate submarine H. L. Hunley was the first to sink an enemy ship in combat. The Hunley rammed its spar torpedo (an explosive charge on the end of a long pole attached to the Hunley) into the hull of the Union screw sloop USS Housatonic in Charleston Harbor, Charleston, South Carolina. After successfully planting the charge, she backed away from the Housatonic, paying out a 150' long detonation rope which set off the charge after they had reached that distance away from the Housatonic's hull.

For many years, it was thought that the concussion wave from the spar torpedo's blast sank the Hunley. However, the wreck of the Hunley was discovered some distance from the location of the Housatonic attack, and since her salvage a few years ago (she was raised completely intact and brought to the former Charleston Naval Shipyard for preservation and restoration), it has since been determined that not only did she survive the attack, she was on her way back to base when her crew apparently succumbed to lack of oxygen, and not flooding as had been previously believed. Forensic examination of crew remains confirmed this.