Yahweh thunders his voice before his army; for his forces are very great; for he is strong who obeys his command; for the day of Yahweh is great and very awesome, and who can endure it?
And the LORD shall utter his voice before his army: for his camp [is] very great: for [he is] strong that executeth his word: for the day of the LORD [is] great and very terrible; and who can abide it? (h) The Lord will stir up the Assyrians to execute his judgments.
The words are certainly exaggerated, the earth could only quake when locusts settled, the heavens only darken when flying. But לפניו refers to the locusts themselves, not merely to a storm or to Jehovah's coming, and Joel is describing the plague's terror, not explaining it away as subjective fear. The whole creation trembles at God's judgment.
AI summary
Commenting on Joel 2:10-11
Lord . . . his army--So among Mohammedans, "Lord of the locusts" is a title of God. his voice--His word of command to the locusts, and to the antitypical human foes of Judea, as "His army." strong that executeth his word-- (Rev 18:8).