The U.S. launched an airstrike against ISIS near Baghdad on Monday — a move that a defense official told NBC News marked the start of the intensifying offensive by Washington against the Islamist militant group in Iraq. The U.S. attack hit an ISIS fighting position southwest of the capital in support of the Iraqi security forces, defense officials said. This specific airstrike was more offensive in nature and was not triggered by any advance of ISIS toward the Iraqi capital, the official said.