Revelation 7:1 And after these things I saw four angels standing on the four corners of the earth, holding the four winds of the earth, that the wind should not blow on the earth, nor on the sea, nor on any tree.
2 And I saw another angel ascending from the east, having the seal of the living God: and he cried with a loud voice to the four angels, to whom it was given to hurt the earth and the sea,
3 Saying, Hurt not the earth, neither the sea, nor the trees, till we have sealed the servants of our God in their foreheads.
Chapter 7 begins kind of taking a step backwards but still holding to the things that have taken place, again most of the destruction has taken place because of the antichrist and man himself and not by the hand of God. Now God is letting you know that before He begins to pour out His wrath upon the earth he will seal the 144000 to protect them while they still preach to all to repent. They are sealed by God to keep them from any harm till God calls them home.