But first, that daring delta force raid deep inside Syria, they set out to capture Abu sayyaf, the man in charge of funding Isis, he was killed in the firefight, but U.S. Forces did capture his wife... See More
But first, that daring delta force raid deep inside Syria, they set out to capture Abu sayyaf, the man in charge of funding Isis, he was killed in the firefight, but U.S. Forces did capture his wife and key intelligence and ABC's terry Moran reporting on the raid and terry, this was a risky operation. Reporter: It certainly was, good morning, George, it was high-risk operations sending these American troops deep into the heart of isis-controlled territory in Syria. But the president decided that the intelligence was good enough, the target valuable enough, and the delta force troops lethal enough to roll the dice here. The daring raid happened overnight Friday. The elite delta force troops taking off from Iraq, heading deep into Syria. Their mission -- capture and interrogate Abu sayyaf. Isis' top moneyman. Former special forces officer Jim gavrilis. This is not just another person. Reporter: A counterterrorism official tells ABC news that sayyaf is believed to be the Isis leader to be given American hostage Kayla Mueller as a forced bride or slave. The question on many minds after thousands of air strikes on Isis targets. Why risk a dangerous ground operation? We really wanted to capture him, no question about that. He could have given a lot of information about their whole financial structure. Reporter: But fate would have otherwise. On the ground at sayyaf's house, a fierce firefight. Isis defending the building, using women and children as human shields, the Pentagon said. Alt time, combat so close, commanders using hand to hand training. It happens in close quarter battles. They'll even duck under their rifle. Reporter: Abu sayyaf killed in the firefight. Say rafa's captured, held for questioning. All American personnel returned safely after scooping up laptop computers that could prove to be an intelligence windfall. The raid comes as Isis has been making gains in recents in ramadi. What happened to sayyaf this weekend sends a unmistakable message to Isis leaders, U.S. Intelligence is improving and they're not safe anywhere. Okay, terry, thanks. More on this from Michael Morell. Mr. Morell, thank you for joining us this morning. Take us inside the decisionmaking this morning. Is it a success even though Abu sayyaf killed not captured? So, George, really important here, the real value here is taking a guy off the battlefield who's incredibly important to the organization, to funding it, to running it, very close to the senior leadership, taking him off the battlefield very important. It would have been great to keep him alive and questioned him, but his wife worked very closely with him. She'll be able to tell us a lot, George. Those computers, that information we got is going to help us understand the organization better, unravel it. In your new book, you explain some of the intelligence files picked up after the 2014 raids deep inside Syria, we learned about the ambitions of Isis there. Two documents in that cache was is how effective weapons of maz destruction can be. That is us. And how you make bubonic plague and used that against the enemy, and that is us. The religious justification for using weapons of mass destruction. We could be learning more from these new files. As terry mentioned, Isis taking hold of ramadi right now, what is your judgment on where the war stands right now and the most important thing that the United States needs to be doing? So, George, number one, we have taken back about 25% of the territory that Isis took in Iraq, still a lot more work to be done but we are doing well in Iraq. It's Syria where we need to do better, there aren't troops on the ground in Syria, there's not a way to take back territory in Syria right now, this raid sends a message. But we'll have to take back territory in Syria as well as Iraq. What is your greatest fear from Isis? I think what we just talked about, an attack in the homeland, using some sort of weapons of mass destruction. If they get a safe haven and they get it over the long term, those are the kind of things we have to worry about, George. Thank you, Michael Morell.
This transcript has been automatically generated and may not be 100% accurate.