With Iraqis reeling-casualties, desertions, and other effects of the air campaign-the coalition launches its ground campaign, which (supported heavily by airpower) is concluded in just 100 hours.
The U.S. began extensive air and artillery strikes against Islamic State group targets in Syria on Dec. 19 in retaliation for the killing of three Americans on Dec. 13 by a gunman affiliated with ISIS, U.S. officials said.
