Tesla's secret weapon
A particle-beam weapon uses a high-energy beam of atomic or subatomic particles to damage the target by disrupting its atomic and molecular structure. A particle-beam weapon is a type of directed-energy weapon, which directs energy in a particular and focused direction using particles with negligible mass.
Tesla gives the following description concerning the particle gun's operation: "[The gun would] send concentrated beams of particles through the free air, of such tremendous energy that they will bring down a fleet of 10,000 enemy airplanes at a distance of 200 miles from a defending nation's border and will cause armies to drop dead in their tracks"