Question: Hi Bob, One more question. How will the 200 million army which you say are demons kill a third of the worlds population?
Response: Yes, the 200 million of Revelation 9:13ff. are demons, released as part of God's warning judgments upon the earth, the "fifth trumpet" judgment, or "second woe", to be precise. In verse 18 it says that their lethal instruments are "fire, smoke and sulfur", which are described also as "plagues", but this refers to the intensity and fatality of the "blows" they deliver and most likely here does not indicate that these will be in the form of a disease or diseases (as the English word "plague" indicates but the Greek word plege [from which it is admittedly derived] does not). Rather we should see this fire-smoke-brimstone (sulfur) combination as exactly what the angels rained down on Sodom and Gomorrah at the Lord's behest (compare Gen.19:24 with 19:22, 19:13 and 18:32; cf. 2Ki.1:10ff; Rev.11:5), and which the demons rained down upon Job's possessions with God's permission (Job 1:16; cf. Rev.13:13). This supernaturally caused natural destruction (i.e., fiery explosions, a perfectly natural phenomenon but with a supernatural origin) is an important transition in the ramping up of judgment to warn the inhabitants of the earth to change their ways and turn to God. The first four trumpets introduce judgments which could be entirely explained away as "natural phenomena", but now we have one which, while it comes through natural media, must be of supernatural origin (fire, smoke and brimstone don't just rain down from heaven naturally). This second "woe" is also contemporaneous with the bulk of the ministry of the two witnesses, Moses and Elijah, in which they direct similar judgments upon the earth (though from an entirely divine source) - judgments with natural effects, but clearly supernatural in origin because they come "on call" (Rev.11:6; compare Elijah and the drought and Moses and the ten plagues). This process of intensifying judgment will reach its crescendo in the "third woe", the coming down to earth of the devil and his forces and their personal direction of events in the person of antichrist and his confederacy (Rev.12:12).
This topic is now covered in detail in Coming Tribulation part 3A: "The First Woe"
Yours in Christ,