Joel 1:1 - 2:9 describes a great army coming against Israel. I will pluck out a few verses for information gathering purposes. (LXX version)
Joel 1:5 “Awake, you drunkards, from your wine, and weep: mourn, all you that drink wine to drunkenness: for joy and gladness and removed are from your mouth. 6 For a strong and innumerable nation is come up against My land, their teeth are lion’s teeth, and their back teeth those of a lion’s cub. 7 They have ruined My vine, and utterly broken My fig-trees: they have utterly searched My vine, and cast it down; they have peeled its branches.
Joel 1:9 The meat-offering and drink-offering are removed from the house of Yehovah: mourn, you priests that serve at the altar of Yehovah. ... 13 “Gird yourselves with sackcloth, and lament, you priests: mourn, you that serve at the altar: go in, sleep in sackcloth, you that minister to God: for the meat-offering and drink-offering are withheld from the house of your God. ... 16 Your meat has been destroyed before your eyes, joy and gladness from out of the house of your God.
There must be a Temple, sacrifices, etc. when this army comes.
Joel 1:11 the farmers are consumed: mourn your property on account of the wheat and barley; for the harvest has perished from off the field.
Must be an early Springtime event.
Joel 1:15 Alas, Alas, Alas for the day! For the day of Yehovah is near, and it will come as trouble upon trouble. ... 2:1 “Sound the trumpet in Zion, make a proclamation in My holy mountain, and let all the inhabitants of the land be confounded: for the day of Yehovah is near
The Day of the Lord is near, not here. So, it seems this will occur just before the Day of the Lord.
Joel 2:2 ... a numerous and strong people shall be spread upon the mountains as the morning; there has not been from the beginning one like it, and after it there shall not be again even to the years of many generations.
A unique event that has never happened before, not will happen again, for at least many generations.
Joel 2:3 Before them is a consuming fire, and behind them is a flame kindled: the land before them is as a paradise of delight, and behind them a desolate plain:
NKJV 2:3 A fire devours before them, And behind them a flame burns; The land is like the Garden of Eden before them, And behind them a desolate wilderness
This occurs at a time of great peace and prosperity. Then, the land is desolate when they leave.
Joel 2:4 Their appearance is as the appearance of horses; and as horsemen, so shall they pursue. 5 As the sound of chariots on the tops of mountains shall they leap, and as the sound of a flame of fire devouring stubble, and as a numerous and strong people setting themselves in array for battle. 6 Before them shall the people be crushed: every face shall be as the blackness of a cauldron. 7 As warriors shall they run, and as men of war shall they mount on the walls; and each shall move in his right path, and they shall not turn aside from their tracks: 8 and not one shall stand aloof from his brother: they shall go on weighed down with their arms, and they fall upon their weapons, yet shall they in no way be destroyed. 9 They shall seize upon the city, and run upon the walls, and go up upon the houses, and enter in through the windows as thieves.
They appear as horses and horsemen, yet they cannot be harmed by any weapons. Leaping on to tops of mountains? Entering windows like thieves? Are these people?
Joel 2:10 Before them the earth shall be confounded, and the sky shall be shaken: the sun and the moon shall be darkened, and the stars shall withdraw their light. 11 And Yehovah shall utter His voice before His host: for His camp is very great: for the execution of His word is mighty. For the day of Yehovah is great, very glorious, and who shall be able to resist it?
It appears that the great army is the host of heaven, and not a human army. Though, I do note that this is the Day of the Lord. Whereas earlier, the Day of the Lord was near. So, there could be a difference.
Joel 2:13 And rend your hearts, and not your garments, and turn to Yehovah your God: for He is merciful and compassionate, long-suffering, and plentiful in mercy, and repents of evils. 14 Who knows if He will return, and repent, and leave a blessing behind Him, even a meat-offering and a drink-offering to Yehovah your God?”
It certainly appears that Yehovah is leading this army Himself. "He may return and leave a blessing behind Him."
Joel 2:15 Sound the trumpet in Zion, sanctify a fast, proclaim a solemn service: 16 gather the people, sanctify the congregation, assemble the elders, gather the infants at the breast: let the Bridegroom go forth of His chamber, and the bride out of her closet.
Perhaps, the coming of the Bridegroom that Jesus talked about in Matthew 25?
Temple in place. Early springtime event. Prior to the Day of the Lord. A time of peace and prosperity. (Perhaps, the "peace and safety" Paul talked about?) A unique event that has never happened before.
What is this great army? Where/when does it fit into your understanding of prophecy? Thanks.