If , as some reports suggest, Islamic State forces have seized Mosul Dam, they might have stumbled on a weapon exponentially more powerful than any U.S.-made armored vehicle or Soviet-era anti-aircraft gun.

The Mosul Dam is Iraq’s largest dam and with its shoddy construction could, if destabilized, affect the lives of Iraqis as far south as Baghdad.

Located on Mosul Lake the facility provides electricity and irrigation to surrounding areas.

“If the dam fails, scientists say, Mosul could be completely flooded within hours and a 15-foot wall of water could crash into Baghdad,” Keith Johnson wrote in a Foreign Policy article from earlier this summer.

A 2011 article from the International Water Power and Dam Construction magazine indicated that if the Mosul Dam was destroyed the ensuing destruction could result in half a million deaths.

In July the Islamic State took the Nuaimiyah Dam in Western Iraq, and now with the seizure of the Mosul Dam, its control of critical infrastructure presents a huge challenge for the the Iraqi government.

In a 2007 letter to Iraqi Prime minister Nouri al-Maliki from then commanding General of the U.S. Army David Petraeus and U.S. ambassador to Iraq Ryan Crocker, the two Americans warned that the structure, built in the 1980s, had been erected on an unstable foundation of soil and was “at great risk of failure.”

Johnson described Iraq’s dams as the country’s “soft underbelly in the fight against ISIS. ”

Iraqi forces remain in control of Haditha Dam. That structure, a sprawling hydro-electric facility located to the south west of Baghdad in Al-Anbar province, was a key focus of coalition efforts during the Iraq war. For most of the U.S. occupation of the country a large contingent of Marines were physically garrisoned within the structure.

“Using [the] Haditha [dam], ISIS could flood farmland and disrupt drinking water supplies like it did with a smaller dam near Fallujah this spring,” Johnson wrote, referring to a flood that displaced more than 50,000 people between Fallujah and Abu Ghraib.