Revelation 6:7-8

7 And when he had opened the fourth seal, I heard the voice of the fourth beast say, Come and see.

8 And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him. And power was given unto them over the fourth part of the earth, to kill with sword, and with hunger, and with death, and with the beasts of the earth.

When the fourth seal is opened, the fourth creature that is around the throne tells John to go and see. John sees a sickly pale green horse. (The Greek word  clwrov  (chloros) is used and it is more likely to be translated as green than pale). The rider on him brought death and Hades follows with him. The passage implies that when this rider rides there will be hell on earth and that possibly this rider has some control over the underworld. The passage says that power was given to kill with weapons, lack of food, death (plague) and with savage animals of the earth. God allows sword, famine, wild beasts and pestilence to chastise the nations.

2 Samuel 24:13  So Gad came to David, and told him, and said unto him, Shall seven years of famine come unto thee in thy land? or wilt thou flee three months before thine enemies, while they pursue thee? or that there be three days  pestilence  in thy land? now advise, and see what answer I shall return to him that sent me.

Some think the death from the beasts will be pestilences that cross over from animals to man. The passage also indicates that these events will occur on one fourth of the earth s land surface. Disease often accompanies war but here germ warfare is probably also involved. These events may be describing a world war along with civil war that takes place between neo-Christian western nations and Islamic nations that becomes so bad the survivors will be looking for a leader that proposes absolute control of the world through world government and an all inclusive world religion.