Saagar Enjeti on October 19, 2016

U.S. officials expect Islamic State chemical weapons attacks to increase as Iraqi troops advance on the city of Mosul, Reuters reports.

U.S. forces confirmed ISIS used Mustard Gas shells as recently as Oct. 5 against local troops. ISIS also launched chemical weapons at a U.S. base in Iraq in late September. U.S. officials stressed at the time that the mustard gas agent was “ineffective,” of “low purity,” and “poorly weaponized.”

While ISIS’s chemical weapons capability remains nascent, sulfur mustard gas shells can still cause blistering on exposed skin and lungs, if inhaled.” Given ISIL’s reprehensible behavior and flagrant disregard for international standards and norms, this event is not surprising,” a U.S. defense official told Reuters.

Approximately 100 U.S. special operators are embedded with the nearly 100,000 troops currently advancing on Mosul. The Pentagon insists these forces are advising and assisting Iraqi forces, and will not engage in direct combat against ISIS. U.S. Navy Seal Charles Keating was killed in May in a similar advise and assist mission in Iraq, when the Kurdish unit he was attached to came under heavy fire from ISIS militants.

The U.S. has approximately 5,000 U.S. troops in Iraq, with the majority serving in advisory or support roles who remain on base. The role does not keep them from harm’s way, rocket fire killed a Marine on a base in northern Iraq in late March.

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