Most of the exegetic energies directed towards Isaiah 18 are usually directed to the first two or final verse. Identifying the people tall and smooth and guessing at the nature of the gift that they will eventually bring has absorbed much energy and even produced a book. However the middle four verses of this chapter also provide useful insight into the time that exists leading up to the final judgment of the nations. It is to this period that this brief essay is addressed.
Isaiah 18:3 addresses the nations of the world and tells them that they should be looking for the coming of judgment which will be announced by an ensign and a trumpet. The ensign is characteristic of Isaiah and is shown to be Christ. Of course this lifting up could refer to the first advent when he was lifted up to die or it could refer to the second. However the trumpet blowing is far more characteristic of the Second Advent. It would appear that that Isaiah 18:3 is taking us to the end of times when the Lord Himself comes in judgment.
Isaiah 18:4 then gives us an interesting insight into the present time. The Lord is essentially resting and watching from His dwelling place. That is not to say He is idle; the remainder of the verse makes clear that He is still having two very different yet subtle effects. Sometimes He is the clear heat on a sunny day; not necessarily the brilliance that draws attention but the UV that can slowly burn you up. Other times though he is like the cool dew on a hot day; that incongruous blessing that does not really appear to fit with the environment. And so today the influence of God in blessing or curse continues but not in the overt manner that it once was or one day will be.
I believe that Isaiah 18:4-5 need to be taken together for the full force of them to be understood. Some view verse four as referring to a form of fruit thinning. That is to say the less productive twigs are thinned from the vine. This is an entirely legitimate thing to do horticulturally. However cutting down the branches before the harvest is very unusual. Also it is not entirely clear how the unproductive twigs would yield enough food to feed the birds for an entire year.
I think something very different is happening. Once the vine has budded and the early fruit is formed the vine tender has a reasonable expectation of the harvest he will get. What is happening here is that the harvest is occurring sooner than expected. Further the vine is being butchered to prevent any further harvest from occurring. I suggest this is directly equivalent to the harvest of the vine in Revelation 14. I don't think this is careful tinkering at all; I think it is wholesale butchery.
In conclusion then we have seen the middle of Isaiah 18 contains a précis of the time in which we live and details how it will end. For now God is resting from His more overt works. He is watching from His dwelling and is acting, at least judicially, through subtle and somewhat indirect methods. There will come a point when Christ is raised up and the trumpet will sound and the time of direct action will be once again. Then the vine of the earth will be butchered swiftly and brutally and against all timing and expectations of those that presently tend it.