The United States expects the Islamic State group to use crude chemical weapons as it tries to repel an Iraqi-led offensive on the city of Mosul, U.S. officials say, although adding that the group's technical ability to develop such weapons is highly limited.
U.S. forces have begun to regularly collect shell fragments to test for possible chemical agents, given the Islamic State group's use of mustard agent in the months before Monday's launch of the Mosul offensive, one official said.
In a previously undisclosed incident, U.S. forces confirmed the presence of a sulfur mustard agent on IS munition fragments on Oct. 5, a second official said. IS militants had targeted local forces, not U.S. or coalition troops.