U.S. aircraft struck Islamic State targets Wednesday inside Mosul, the heart of militant operations in Iraq and the country’s second most populous city, the Defense Department said.

The operation, which the military said destroyed four vehicles used by the militants and damaged two others, marked a significant change in coalition operations that have tended to stay outside heavily populated areas to avoid civilian casualties.

“In this particular case, it met the criteria we needed to make the strike,” said a Defense Department official, who spoke on the condition of anonymity about details beyond the official statement from U.S. Central Command. […]