‘For Yahweh has indignation against all the nations,
And fury against all their host.
He has utterly destroyed them (put them under the Ban, devoted them),
He has delivered them to the slaughter.
Their slain also will be cast out,
And the stink of their carcases will come up,
And the mountains will be melted with their blood.'
The fact that the nations have been called on to witness this and are having it explained to them, and that the total judgment of ‘all the nations' mentioned here is described in a way that seems to single them out (He has called on the other nations to witness it), suggests that ‘all the nations' here cannot mean all the nations of the whole known world. It is ‘all the nations' of the particular area under judgment, that is, it is Edom and her allies known under that name, although possibly as a warning to all nations. It would be a particularly useful way of describing Moab and Ammon and the variety of nomadic tribes in the desert, including Amalek, that connected with Edom, and often allied with her, seen in Isaiah 34:5 as ‘the people of my curse' (compare Exodus 17:14; Exodus 17:16; Exodus 25:17-19; Deuteronomy 23:3-6; Nehemiah 13:1-3). Compare how in Isaiah 63:6 His judgment on Edom also affects ‘the peoples'. The use of the term ‘the nations' in this way, as limited to a particular area, is exemplified in Isaiah 9:1; Judges 4:2; see also 2 Chronicles 32:23; Ezekiel 5:5; Ezekiel 5:7; Nehemiah 5:17; Nehemiah 6:16, although not there as referring to these same tribes.
‘All their host.' This suggests that these nations have gathered together their fighting men to take advantage of Judah's weak condition. Such were the ways of the world that during times of trouble for a nation their neighbours would often look out for ways of benefiting from it.
But others see ‘all the nations' as meaning exactly that and the restriction to Edom that follows as therefore being because it is about to be used as an example of the judgment God will bring on all. However, the particularisation of the judgment as against Edom in the way that is described does not seem to support this case. It is Edom particularly (with her allies) who are to be subjected to great slaughter, and whose land is to be drunk with blood (Isaiah 34:6), and who are to be finally extinguished (Isaiah 34:9-10). It is they who are to be the example to the nations. On the other hand this kind of half-anonymity is typical of Isaiah (compare chapter 13 of Babylon). The hint seems to be that what applies to the particular situation could apply to all, even in fact to the hosts of heaven as well (Isaiah 34:4-5 a). For all are finally under the judgment of God.
The total destruction of these nations is vividly described. In His anger they are put under The Ban, ‘devoted' to destruction. They are delivered to slaughter (specifically said of Edom in Isaiah 34:6). They will not be given proper burial, but will be ‘cast out' and left in stinking piles in the mountains to rot (compare Isaiah 14:19-20 of the king of Babylon).
‘And the mountains will be melted with their blood.' So great will be the number of their dead that the blood spilled will cause soil erosion in the mountains. As so often in prophecy the perfect (definite) tenses indicates not the past but the certainty of what is to happen. It is already seen as completed in the mind if God.