John Calvin Commentary Isaiah 34:2

"For Jehovah hath indignation against all the nations, and wrath against all their host: he hath utterly destroyed them, he hath delivered them to the slaughter." — Isaiah 34:2 (ASV)

For the indignation of Jehovah is on all the nations. He undoubtedly means “the nations” that were hostile to the Jews, and at the same time were neighboring them; for, being surrounded on all sides by various nations, they had almost as many enemies as neighbors. Though this hatred arose from other causes, such as envy, yet the diversity of religion greatly inflamed their rage, for they were extremely offended at having their superstitions condemned. This provided an even stronger reason why God promised that He would be a judge and avenger.

On all their army. This is added because the Jews were few in number when compared with the rest of the nations. Therefore, although “the nations” were proud of their vast numbers and despised the Jews because they were few, yet he declares that God will easily diminish and crush them, in order to preserve His little flock, of which He is the guardian.

He hath destroyed them. Though he speaks of future events, yet he chose to employ the past tense, in order to place the event immediately before the eyes of those who were lying low and overwhelmed with adversity. These predictions were made, as I briefly noted earlier, not on account of the Edomites, who paid no attention to this doctrine, but for the sake of the godly, whom He wished to comfort, because they were miserably harassed by their enemies.