As Iraq’s second-largest city and an Islamic State stronghold since June 2014, Mosul has seen heavy fighting in recent weeks as Iraqi and Kurdish troops have advanced from multiple directions in an attempt to retake it. The Islamic State has used snipers, anti-tank guided missiles and car bombs in an effort to stymie the offensive, but the group has yet to use any conventional chemical weapons as forces enter the city. Internationally condemned, chemical weapons are strictly regulated by international arms treaties.
The Islamic State did, however, set fire to a nearly burnt out sulfur mine roughly 25 miles southeast of Mosul as the campaign to retake the city began in earnest. As the wind shifted, the noxious fumes wafted over nearby U.S. troops and civilians displaced from the city, causing the troops to don gas masks and incapacitating hundreds of the unprotected civilians with nose bleeds, headaches and choking fits. Iraqi forces put out the fire within a week.
“As the Islamic State loses ground around Mosul, there is a high risk of the group using chemical weapons to slow down and demoralize advancing enemy forces, and to potentially make an example of — and take revenge on — civilian dissidents within the city,” said Columb Strack, senior analyst and head of the IHS Conflict Monitor, in the report.
Since 2014, the Islamic State has used chemical weapons 19 times around Mosul. However, before the Iraqi offensive on the city, chemical attacks declined, the report said. This is probably because the group’s chemical weapons technicians and experts were evacuated to Syria, the report added. Atop the possible loss of chemical-weapons talent from the city, the U.S.-led air campaign in Iraq and Syria has also heavily targeted Islamic State chemical weapons facilities in Iraq in recent months. In March, U.S. Special Operations forces captured the group’s top chemical weapons expert during a raid in northern Iraq.
The Islamic State has used chemical weapons, namely sulphur mustard agents, haphazardly throughout its campaigns in Iraq and Syria, striking indiscriminately against entrenched forces and civilian areas. The group has also used chlorine in certain munitions. An industrial chemical, chlorine has been used in numerous attacks by both the Islamic State and Syrian government forces. Chlorine, when inhaled, can cause difficulty breathing.
In September, a shell fired at a U.S. air base in northern Iraq initially tested positive for containing a mustard agent but was ultimately inconclusive. There were no U.S. casualties in the attack.
Usually thought to be a gas, mustard agent is usually stored as an oily liquid and can cause blindness and burns to the respiratory system upon inhalation. Exposure to large quantities can be lethal. While U.S. troops deploy with proper equipment to shield themselves from chemical attacks, local forces — such as Iraqi troops and Kurdish peshmerga — are often lacking when it comes to protective gear. Civilian populations in contested areas also have few ways to protect themselves if they are hit by an errant shell or specifically targeted.