Revelation 9:15-18

The four angels were released. War is in God's decree (even though it is Satan who actually brings it); and the hour, day, month, and year are fixed. These angels are allowed to kill one third of all mankind - horrible, yet limited. John sees in the vision the armies on the battlefield. There are so many troops he cannot count them, but he is told there are 200 million (a symbolic number); and these mounted troops and horses have but one purpose - to destroy! In the vision, the mounted troops and the horses work together so well, that the colors of the breastplates and the fire, smoke, and sulphur coming from the horses' mouths, match each other. Fire, symbolic of destruction. Sapphire, symbolic of suffering. Sulphur, symbolic of torture. These symbolize the destructive machines of war, the bombs etc., the defoliating chemicals, poison gas, etc. - all the things which man uses to kill each other in battle.