Simply WMDs from Iraq that weren’t shipped by Russia to Syria.
See also the following previous posts for further information:
How Did Syria Acquire Massive Stockpiles of WMD?
FLASHBACK: UN inspectors: Saddam shipped out WMD to Syria before war and after
Facility containing disused stores of sarin and mustard gas overrun by jihadist group
The jihadist group bringing terror to Iraq overran a Saddam Hussein chemical weapons complex on Thursday, gaining access to disused stores of hundreds of tonnes of potentially deadly poisons including mustard gas and sarin. Continue reading