The rider of the second horse is taken to represent War. His horse is red. The color red, and the rider's possession of a great sword, suggests blood. | The first horseman is called Pestilence, and is associated with infectious disease and plague. "They were given power over a fourth of the earth to kill by sword, famine, plague, and by the wild beasts of the earth." (Revelation 6:7-8).
"When He broke the second seal, I heard the second living creature saying, “Come.” And another, a red horse, went out; and to him who sat on it, it was granted to take peace from the earth, and that men would slay one another; and a great sword was given to him." (Revelation 6:3-4) |  Albrecht Dürer, Knight, Death and the Devil, 1513 |