Adam Clarke on Joel 1:6

A nation is come up upon my land - That real locusts are intended there can be little doubt; but it is thought that this may be a double prophecy, and that the destruction by the Chaldeans may also be intended, and that the four kinds of locusts mentioned above may mean the four several attacks made on Judea by them. The first in the last year of Nabonassar, (father of Nebuchadnezzar), which was the third of Jehoiakim; the second when Jehoiakim was taken prisoner in the eleventh year of his reign; the third in the ninth year of Zedekiah and the fourth three years after, when Jerusalem was destroyed by Nebuchadnezzar. Others say that they mean four powers which have been enemies of the Jews:

1. The palmerworm, the Assyrians and Chaldeans.

2. The locust, the Persians and Medes.

3. The cankerworm, the Greeks, and particularly Antiochus Epiphanes.

4. The caterpillar, the Romans.

Others make them four kings; Tiglath-pileser, Shalmaneser, Sennacherib, and Nebuchadnezzar. But of such similitudes there is no end; and the best of them is arbitrary and precarious.