Steven Ben Noon is asking if this is describing aliens? I have yet to sit through the entire video clip of Steven's but it got me thinking hard. If one believes in the prophecies given by young Nathan, then this passage is describing the USA. I say this because of the hints this scripture is giving us. The nation and people described are feared far and wide (who is the most powerful, aggressive nation on earth today?) an aggressive nation of strange speech (not Hebrew) whose land is divided by rivers. Isaiah 18: 3 - 4 says:

"All you people of the world, you who live on the earth, when a banner is raised on the mountains, you will see it, and when a trumpet sounds, you will hear it". Then in Isaiah 18: 4 - 5

" The LORD said to me, " I will remain quiet and will look on from my dwelling place, like shimmering heat in the sunshine, like a cloud of dew in the heat of harvest". For, before the harvest, when the blossom has gone and the flower becomes a ripening grape, he will cut off the shoots with pruning knives and cut down and take away the spreading branches. They will all be left to the mountain birds of prey and to the wild animals; the birds will feed on them all summer, the wild animals all winter".

God tells Isaiah that the entire world will witness the banner raised on the mountains and hear the trumpet sound. God describes Himself as watching and waiting in what can only described as a hot day. Shimmering heat in the sunshine. The heat will be high, like it is in the heat of harvest. Then a huge heads up for the time of year is given: - This will happen BEFORE harvest time. It sounds like end of spring going into early summer.  The flower has gone but before it becomes a ripening grape.. Then, I believe we are given a rapture heads up. "He will cut off the shoots with pruning knives and CUT DOWN and TAKE AWAY the spreading branches. The church is described as branches grafted onto the root stock of Israel (see Roman 11:11 - 31. Link below) So - the branches are cut down and taken away. The rest will all be left to the mountain birds of prey and to the wild animals. Another big, fat hint as to the time of year this all takes place is that we are told that the birds will feed on them all summer, the wild beasts all winter. Therefore, this happens at the end of spring - when the blossom has just gone.

Bible Gateway passage: Isaiah 18 - New International Version