The theme of the Book of Joel is the coming of the great and mighty "Day of the Lord" (it is used 6 times in the short book). Joel was a prophet of God in Judah and Israel in about 900 B.C . Little is known about his life. He may have been a farmer (like Amos) since his allusions involve land and crops. However, he prophesied some of the most poignant scriptures about the judgments, the army of the Lord and the mercies of God.
Joel 2 is traditionally interpreted as the story of a locust swarm that devastated Israel (Joel 2:1-11). However, a closer reading, and a little revelation from God, reveals it to mean something different, something deeper. Although Joel may have seen a locust swarm devour Israel's crops, he uses the event allegorically to convey something more important than a locust swarm.
In Joel 2, the prophet is actually describing the army of the Lord in the end-time. He sees the army executing God's judgments in the Day of the Lord. He outlines an escape from the judgments by the people and he ends with the mercy that God will show to his remnant.
He begins his description of the Army of the Lord in verse Chapter 2, verses 2-3:
"So there is a great and mighty people;
there has never been anything like it
Nor will there be after it...
A fire consumes before them
behind them a flame burns
The land is like a Garden of Eden before them
But a desolate wilderness behind them,
and nothing at all escapes them" (v.3).
Joel speaks of a "great and mighty people" who go through the land executing judgments. The promise of a Garden of Eden is before them but a desolate wilderness of destruction (judgment) is behind them. They are like "a people arraigned for battle" (v.5). All faces turn pale, (that is the unrepentant whom God is destroying) . The army runs like mighty men, climbs the wall like soldiers, they each march in their own line, everyone in his own path (organized) and they don't deviate from their goal (v. 6-7).
"The Lord utters his voice before his army and strong is He who carries out his Word" (of judgment). Joel 2:11.
He holds his hand out to Israel:
"Yet even now" [in the midst of the destruction] God says to the people:
"Return to me with all your heart...and rend your heart not your garments [rending garments was traditional in repentance in Israel]..."who knows whether the Lord will not turn and relent" (v.12-14). Even in the midst of terrible judgment, God still urges His people to repent.
In verses 15-27, God enumerates (through His prophet Joel) the many blessings He has for the people who turn to Him.
Finally, in ending Joel 2, Joel prophecies as to what God is going to do in the end-time:
"...I will pour out My Spirit on all mankind;
and your sons and daughters will prophesy,
your old men will dream dreams
your young men will see visions....I will display wonders in the sky and on the earth,
blood, fire and columns of smoke...
Before the great and awesome day of the Lord.
And it will come about that whoever calls on the name of the Lord will be delivered; for on Mt. Zion and in Jerusalem There will be those who escape" (v. 28-32).
So Joel 2 can be summarized this way. The wickedness of the people had become so great that God once again had to send judgment upon the earth, through His end-time army, of which all real believers are a part. They have a vision of paradise before and destruction is behind them. They are led only by the voice of God. They are organized; nobody doing their own thing. And yet during all this God still promises blessings on all who turn to him. And he will pour out His Spirit "on all flesh", not just Israel. And "whoever" calls on the name of the Lord will be saved.