The United States has initiated airstrikes on Islamic militants in Iraq who threaten fleeing civilians. But what precisely are we attacking? Likely a lot of stuff we built, sold and shipped over there during our long war to keep Iraqis safe, at least one expert says.

Defense News' Paul McLeary explains how the Islamic State—the fast-moving offspring of Al Qaeda in Iraq, often still referred to as the Islamic State in Iraq and the Levant (ISIL)—got hold of Uncle Sam's heavy artillery, literally:

When the Iraqi Army's 2nd Division broke and fled ahead of the advancing columns of ISIL fighters near Mosul earlier this summer, they left behind a treasure trove of US supplied military equipment that the jihadists have since turned on the civilian population.

Among the spoils were hundreds of Humvees, small arms and ammunition, and as many as 52 American M198 howitzer mobile gun systems – the same guns that two US Navy F/A-18s likely pounded with 500 lb. laser guided bombs on Friday.

The mobile gun systems were in rage of the city of Irbil, which president Obama said on Thursday night that the United States would fight to protect, as about 40 US military personnel are there manning a joint operations center with Iraqi forces, along with American diplomats and civilians working at the consulate there.

There's an even deeper irony: Gen. Lloyd Austin—the general in charge of U.S. Central Command, which is tasked with organizing the current strikes in Iraq—was in charge of Multinational Corps Iraq, the command that ran the U.S.-led war's day-to-day operations, in 2008 and 2009. Which means that Austin is now overseeing the bombing of materiel that he and his troops probably fought alongside in those late years of the war.

Sigh.

If you're dying to know more about the IS fighters, their brutal methods, and their rock-star recruiting drives among teens, watch the VICE News video above, in which reporter Medyan Dairieh embeds with the Islamic State. Really.