Some of the first anti-personnel devices created in Korea were comprised of small rockets attached to arrows, which flung spikes upon detonation. When it was discovered that several of these rockets could be launched from the same container, larger versions of these anti-personnel devices were created and utilized in battle. These larger anti-personnel devices were designed to be transported on wheeled vehicles such as a two-wheeled carts and wheelbarrows. The Hwach'a, which was invented in 1451, allowed a single man to transport approximately 100 rockets into battle, and was well suited to combat the invading Japanese Samurai who typically advanced on the Koreans in dense groups, presenting ideal targets for the Hwach'a operators.