Thomas Aquinas Commentary Lamentations 2:5

"The Lord is become as an enemy, he hath swallowed up Israel; He hath swallowed up all her palaces, he hath destroyed his strongholds; And he hath multiplied in the daughter of Judah mourning and lamentation." — Lamentations 2:5 (ASV)

Here he weeps over the destruction of the buildings used for defense, and he addresses this in three ways.

1. He touches on God's indignation: he has become as an enemy, as if God were helping their enemies in the fight. He was turned to be their enemy, and he fought against them (Isaiah 63:10).
2. He discusses the destruction of the buildings: he has overthrown all the walls. You have broken down all his hedges (Psalms 89:40).
3. He concludes with the humiliation of the people: he has filled, that is, multiplied, their humiliation. Our soul is humbled down to the dust: our belly cleaves to the earth (Psalms 44:25).