While brainstorming how to defend the Philippines from an enemy attack, Bradley A. Fiske invented the aerial form of these weapons.  
During the Civil War, E. C. Singer developed one of these things that attached to a 40-foot-long pole known as the "spar" variety.  The first modern example of one of these devices was powered by a tank of compressed air, had tapered ends, and was designed for the Austro-Hungarian Empire by the Englishman Robert Whitehead.  During World War II, the Japanese developed extremely (*) fast versions of this weapon known as the "long lance", which also contained a deadly magnetic pistol.  While brainstorming how to defend the Philippines from an enemy attack, Bradley A. Fiske invented the aerial form of these weapons.  The automatically-adjusting horizontal rudders on these weapons were eventually replaced by gyroscopes to keep them at a consistent depth.  Protection against these weapons was offered by Destroyers in convoys.  For 10 points, name these principle weapons of U-Boats.
During the Civil War, E. C. Singer developed one of these things that attached to a 40-foot-long pole known as the "spar" variety.  
naval torpedoes [or spar torpedoes or locomotive torpedoes; do not accept "naval mines"]