Albert Barnes Commentary Jeremiah 50:15

"Shout against her round about: she hath submitted herself; her bulwarks are fallen, her walls are thrown down; for it is the vengeance of Jehovah: take vengeance upon her; as she hath done, do unto her." — Jeremiah 50:15 (ASV)

Shout – that is, spoken of the war-cry. So in Isaiah 42:13, where God is compared to a warrior, it is said, He shall shout (the King James Version cry), that is, raise the war-cry.

Site has given her hand – the sign of submission (compare 1 Chronicles 29:24 margin).

Foundations – or, buttresses. The Septuagint: battlements.