Gassing Iraqi Kurds was considered one of Saddam Hussein's most heinous crimes, and American officials now suspect that ISIS is doing the exact same thing—and it may be using Saddam's old weapons. Officials believe the militants used mustard gas, a chemical weapon banned worldwide in 1993, against Kurdish fighters in northern Iraq this week, reports the Wall Street Journal. The group's battlefield use of the agent is obviously an extremely worrying development, officials say, and it's not clear how ISIS obtained it: It could be from one of Saddam's old stockpiles or from stockpiles in Syria, where President Bashar al-Assad claimed in 2013 that all the regime's mustard gas had been destroyed.
"If they do possess these kind of weapons," Democratic Rep. Adam Schiff tells CNN, "my guess is they're more likely to have gotten them as old weapons left over in Iraq from the old WMD program there than they were likely to obtain them in Syria in some kind of a hidden cache of the regime's." ISIS seized the Saddam regime's old chemical weapons plant last year, though officials said at the time that anything left there was probably useless. US officials have downplayed the risk to American personnel in Iraq, saying they're not engaged in combat and, in any case, mustard gas "has to be used in high concentrations to be fatal," the Journal reports. (In the years after the 2003 invasion, the US government covered up how many soldiers were injured by old chemical weapons.)