^9:15 And the four angels who had been prepared for the hour and day and month and year, were released, so that they might kill a third of mankind.

And the four angels who had been prepared for the hour and day and month and year,

God always is prepared even when He will use Satan's henchmen to come upon the earth. He prepared

• the Chaldeans: Habakkuk 1:5-11
• the whale (great fish): Johah 1:17
• the instruments of death: Psalm 7:12-16

And he is precise. The time is exact down to the hour. Or this can be interpreted as the period of time to accomplish the killing. He knows the plan forever - Acts 15:18.

WERE RELEASED, so that they might kill a THIRD of MANKIND.

Death goes out again just where it started -- the Euphrates River -- Cain killed Abel, Genesis 4:1-8. This time, however, 1/3 of mankind are killed (militarily?, see next verse). The sixth TRUMPET kills people; the fifth TRUMPET only harmed men (verse 5).