The Battle of Antietam, the single bloodiest day in American military history, claimed some 3,600 lives, Union and Confederate alike. Meanwhile, the head of Iran’s judiciary promises punishment “without the slightest leniency.” His name is Gholam-Hossein Mohseni-Ejei. So it’s left to the United States to impose meaningful consequences on the Iranian regime for one of the worst atrocities of this century. Last year’s Israeli strikes on Iran’s ballistic missile sites did not keep Iran from restarting production lines once the war had ended. This article originally appeared in The New York Times.