We know because we sold them the stuff when they were fighting with Iran.
IBD
In 2006, former Iraqi general Georges Sada, second in command of the Iraqi Air Force who served under Saddam Hussein before he defected, wrote a comprehensive book, "Saddam's Secrets."
It details how the Iraqi Revolutionary Guard moved weapons of mass destruction into Syria in advance of the U.S.-led action to eliminate Hussein's WMD threat.
As Sada told the New York Sun, two Iraqi Airways Boeings were converted to cargo planes by removing the seats, and special Republican Guard units loaded the planes with chemical weapons materials.
Old news, I know, but please feel free to keep laughing.