ISIS took over a military base in northern Iraq last month that contains Saddam Hussein’s stockpile of chemical weapons, including hundreds of warheads containing sarin and mustard gas.
After the invasion it was said that all of Saddam's WMD had already been destroyed and none remained. If that is the case how did ISIS take control of some just last month? Did we know this stockpiled existed prior to this incident? If not why not? If so then why was it claimed that none existed anymore?
Firstly this is an article with slightly more information: http://www.theguardian.com/world/2014/jul/09/isis-seizes-chemical-weapons-plant-muthanna-iraq
What is states is different from your article in several points:
a) These weapons are from the 80ies (Some usage was in the Iraq-Kuwait war)
Chemical weapons need to be stored properly or they degrade; Both articles claim that the Sarin will be unusable. The guardian further claims the mustard cannot be used for chemical warfare anymore.
b) After the defeat in the first Gulf-war those weapons were dismantled by UN inspectors.
Infact that very bunker complex was used to destroy the chemical weapons of Iraq. As the inspectors left that site before the second Gulf-war and https://www.cia.gov/library/reports/general-reports-1/iraq_wmd_2004/chap5_annxB.html states that it is classified as unusable
So to actually answer your question: There seems to be a mixup of terms. IS (as it now calls itself in offical documents) did not find usable WMD but precursor chemicals and empty warheads. Whether they are able to use those - who knows?
The BBC says:
The Muthanna complex northwest of Baghdad houses remnants of rockets filled with sarin and other deadly nerve agents. The UN and US say the munitions are degraded and the rebels will be unable to make usable chemical arms from them.
The CIA has information about this facility. Apparently, it was declared to the UN as a site where chemical weapons would be dismantled/destroyed or sealed off (for those deemed too dangerous to destroy). There were also sections that collapsed from coalition bombing during the Gulf War, which means there’s the possibility that some nasty stuff is buried in the rubble. A few quotes from the CIA report:
Between 1992 and 1994 and again in 1996, the CDG oversaw destruction of 30,000 pieces of ordnance, 480,000 liters of chemical agents, and more than 2 million liters of chemical precursors. Eventually, most of the facilities at the complex the Iraqi’s destroyed and sold for scrap.
Two Cruciform Bunkers were sealed containing munitions too dangerous for destruction.
Bunkers, damaged by coalition bombing, collapsed, concealing unaccounted CW equipment and munitions in the debris. Over the next ten years some of the facilities were razed by the Iraqis. Precise accountability of equipment and munitions is unverifiable, because the National Monitoring Directorate and UNSCOM did not always oversee excavation.
The final state of the facility, according to the report:
Two wars, sanctions and UNSCOM oversight reduced Iraqi’s premier production facility to a stockpile of old damaged and contaminated chemical munitions(sealed in bunkers), a wasteland full of destroyed chemical munitions, razed structures, and unusable war-ravaged facilities.
I’d avoid Breitbart.com. It seems to be fairly sensationalistic, and saying this facility “contains Saddam Hussein’s stockpile of chemical weapons” is misleading, to say the least.
