John Calvin Commentary Jeremiah 50:30

"Therefore shall her young men fall in her streets, and all her men of war shall be brought to silence in that day, saith Jehovah." — Jeremiah 50:30 (ASV)

He confirms the same thing and shows that the destruction of Babylon would be so complete that everything valuable would be destroyed. Fall, he says, shall her strong men in the streets; which is worse than if he had said, “They shall fall in battle.” Babylon was so taken that all her armed men were killed in the middle of the city. Cyrus indeed spared, as has already been said, the common people; but he killed all the chief men and the armed soldiers. As the Babylonians were taken while keeping a feast, as we read in Daniel, hence Jeremiah mentions the streets.