I realize that many say that this has been fulfilled already:

Joel 2:20 But I will remove far off from you the northern army, and will drive him into a land barren and desolate, with his face toward the east sea, and his hinder part toward the utmost sea, and his stink shall come up, and his ill savour shall come up, because he hath done great things.

But can this also be fulfilled at the time of the tribulation, as well?

If so, then who would be the northern army?

Could that be referring to those who come down upon Israel in Ezekiel 38 & 39?