John Gill Commentary Lamentations 2:3

"He hath cut off in fierce anger all the horn of Israel; He hath drawn back his right hand from before the enemy: And he hath burned up Jacob like a flaming fire, which devoureth round about." — Lamentations 2:3 (ASV)

He has cut off in [his] fierce anger all the horn of Israel , &c.] All its power and strength, especially its kingly power, which is often signified by a horn in Scripture; see (Daniel 7:24); this the Lord took away in his fierce anger, and left the land destitute of all relief, help, defence and protection; whether from its king and princes, or from its men of war or fortified places; all being cut off and destroyed.

he has drawn back his right hand from before the enemy ; either his own right hand, with which he had used to fight for his people, and protect them, but now withdrawing it, left them to the mercy of their enemies; or Israel's right hand, which he so weakened, that they had no power to resist the enemy, and defend themselves.

and he burned against Jacob like a flaming fire [which] devoureth round about ; that is, his wrath was like a burning flaming fire, which consumes all around, wherever it comes; thus the Lord in his anger consumed Jacob, and left neither root nor branch.