Book of Joel Chapter 2 Vs. 20

 The Lord Had Pity

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. Joel 2:20

But I will... The Lord next announced that the threat described in Joel 2:1-11 would be averted (Joel 2:20).

the east sea... The "east sea" could be the Dead Sea or the Euphrates and the Persian Gulf. He would turn against the very army He had been bringing against His disobedient people (cf. Joel 2:11), driving it into the desert (a parched and barren land) and the seas (the eastern sea and the western sea, probably the Dead Sea and the Mediterranean Sea; cf. Zec. 14:8).

the utmost sea... The "utmost sea" is the Mediterranean.

and his stink... The carcasses’ stench would permeate the air. As in Joel 2:1-11, the language, though alluding to a literal army (cf. Isa. 34:3; Amos 4:10), applies to locusts as well. Eyewitness accounts tell how dead locusts, having been driven into the sea and then washed ashore, gave out a foul odor. See Eze. 39:11-16.

Again, The Lord next announced that the threat described in Joel 2:1-11 would be averted (Joel 2:20). He would turn against the very army He had been bringing against His disobedient people (cf. Joel 2:11), driving it into the desert (a parched and barren land) and the seas (the eastern sea and the western sea, probably the Dead Sea and the Mediterranean Sea; cf. Zec. 14:8).

As noted in the Introduction, the designation northern army (lit., “northerner”) suggests that a literal army is ultimately in view. If “the northerner” is yet future (eschatological), the army is possibly the army in Joel 3:9, 3:12; Dan. 11:40; and Zec. 14:2. But if the reference is strictly historical, any precise identification of the army is precluded by the uncertainty surrounding the date of authorship. So in this case it would not be clear to what extent, if any, Joel 2:20 was historically fulfilled in Joel’s day. If the invasion threatened in Joel 2:1-11 had not actually begun, the language of Joel 2:20 need not refer to a historical event. It would simply be a vivid and concrete way of saying that the destruction planned by the Lord had been averted at the last moment.