The U.S. captured the operative in Iraq three weeks ago, the first since a team of Special Operations forces recently began operating in northern Iraq.
Officials told CNN that his name is Sleiman Daoud Al-Bakkar. One official called him "the key leader," but others could not say if he runs the entire chemical weapons program for ISIS.
The information he provided to interrogators has given the U.S. enough information to begin striking ISIS areas in Iraq associated with the group's chemical weapons program. One U.S. official said the goal is to locate, target and carry out strikes that will result in the destruction of ISIS's entire chemical weapons enterprise -- mainly mustard agent ISIS produces itself.
It was not immediately clear if the U.S. was able to strike all of the necessary targets. Intelligence and surveillance of the targets had indicated in some Iraqi locations that civilians were present at prospective sites, officials told CNN.
While the goal is to end ISIS' capability to manufacture and use mustard agent, the actual targets being struck include people, facilities and vehicles. The agent itself is made in relatively small quantities and has a fairly short shelf life, the U.S. government believes.
The program is one the U.S. military has been tracking, with Defense Secretary Ash Carter saying last month the Pentagon was prepared to strike against it.
"It's something we watch very closely and it's something we take action against," Carter said in an interview that aired on PBS.
Since the weekend, the U.S. has struck what it is calling "improvised weapons facilities" and other targets near Mosul, Iraq, but officials would not say if these were chemical weapons sites.
At the request of the Pentagon, CNN initially withheld publishing the detainee's connection to ISIS' chemical weapons program because defense officials said disclosing that would risk alerting ISIS to potential airstrike targets. With the chemical weapons program undisturbed, it would allow ISIS to use the weapons to strike civilians, troops the U.S. supports, and possibly even U.S. troops.
Officials would not explain why they believed the detention itself hadn't jeopardized the airstrikes, or why the U.S. military believes ISIS had not noticed the captured operative had gone missing from its ranks. However, the operative is said to have regularly moved around in Iraq, and officials said they still believe his capture was unknown to ISIS.
U.S. Special Operations forces captured the operative more than three weeks ago. He has been held and interrogated in Irbil, Iraq, for any information he has about the chemical weapons program and the location of other key ISIS personnel or weapons stocks. While there are other ISIS operatives involved in the program, the U.S. believes at this point that the captured man is crucial to understanding this dangerous wing of the organization.
The U.S. has long said any ISIS operatives captured by U.S. troops would only be held for a short time and then turned over to either the Iraqis or the Kurds.
The operative was captured in one of the first missions of the so-called Expeditionary Targeting Forces. It is a group of some 200 Special Operations troops assembled in northern Iraq to gather intelligence and pursue ISIS operatives on the ground by either capturing or killing them in Iraq, and eventually in Syria. Carter recently acknowledged the ETF is "having an effect and operating.
"It's a tool that we introduced as part of our -- the accelerated operations to conduct raids of various kinds, seizing places and people, freeing hostages and prisoners of ISIL, and making it such that ISIL has to fear that anywhere, anytime, it may be struck," he said in late February, using a different name for ISIS.
The U.S. went after this particular individual due to concerns about the "skills and intent" he has, one of the officials said. The mission to capture him was specifically tailored to the location where he was, and was designed to allow troops to be able to seize him. U.S. Special Operations forces were certain he was at the location in Iraq after covertly surveying it for some days.
The U.S. intelligence community has been tracking a number of confirmed chemical attacks by ISIS where powdered mustard agent was used in artillery shells, the official said. The most recent attack was a month ago.
The U.S. intelligence community has confirmed 12 cases of the use of mustard agent. Three other cases are suspected. They include locations in both Syria and Iraq. The majority of the cases have been in Syria, some as far west as the Maraa line where fighting has raged. Other attacks have occurred across Iraq, including Sinjar Mountain and the area around Mosul, as well as locations further south towards Baghdad.
However, U.S. officials are somewhat downplaying the attacks, saying they believe any deaths were a result of being hit by artillery, not the agent itself.
Since interrogations of the detainee began, U.S. Special Operations forces have been using the information he has provided to begin to locate targets.
Under the rules of engagement, U.S. Special Operations forces must have continuous surveillance of a target for a period of time to ensure they know who is there and the locations of any potential nearby civilians before they strike.
The U.S. has said all Special Operations missions are coordinated with the Iraqi government.
Vice President Joe Biden has spoken to Iraqi Prime Minister Haider al-Abadi twice in the last week, though White House readouts of the call did not mention the detainee.
It could not immediately be learned if there were Iraqi forces took part in the raid to capture the man, or whether Iraqis were involved in the airstrikes.
Director of National Intelligence James Clapper recently hinted at the confirmation of chemical attacks by ISIS in congressional testimony.
"Chemical weapons continue to pose a threat in Syria and Iraq," Clapper told the House intelligence committee. "ISIL has also used toxic chemicals in Iraq and Syria, including the blister agent Sulfur Mustard. (It's) the first time an extremist group has produced and used a chemical warfare agent in an attack since Aum Shinrikyo used sarin in Japan in 1995."
Defense officials said this was the first public confirmation by the U.S. government of mustard agent attacks.
The Organization for the Prohibition of Chemical Weapons also continues to track reports of the use of mustard agent and is talking with the U.S. about other possible attacks, U.S. officials said.
Investigators will also want to know whether ISIS has any plans to use chemical agents in attacks against the West. It's unclear whether the captured operative has that knowledge.