Among those captives was James Foley, who was recently beheaded in a gruesome video posted online.
The Wall Street Journal reports his captors originally demanded a ransom of more than $132 million.
U.S. Special Operation Forces launched a daring raid earlier this summer, inside Syria, to try to rescue James Foley and other Americans being held by ISIS.
Dozens of the most elite U.S. commandos from units like Delta Force and Seal Team Six went in by helicopters. Fighters jets and surveillance aircraft provided overhead protection.
The U.S. will not disclose the location, but when the commandos arrived the hostages were not there. Several ISIS operatives were killed. One American slightly injured.
The White House says it demonstrates the U.S. will "spare no effort" to secure the safety of Americans and hold their captors accountable.
Before the operation was revealed, President Obama vowed to be "relentless" in the face of Foley's killing at the hands of ISIS.
"When people harm Americans, anywhere, we do what's necessary to see that justice is done," President Obama said.
British and U.S. Intelligence experts now analyzing every frame of the video for clues about the murder, especially the British accent of the killer.
Foley's parents are calling for peace.
"Jim would never want us to hate or be bitter. We are just very proud of Jimmy," James Foley's Mother Diane Foley said.
So far, ISIS has not made attacking the West a major priority. Now, the killing of Foley is said to be direct retaliation for U.S. airstrikes in Iraq. Airstrikes which are continuing around Mosul Dam, to push ISIS back.
U.S. nerves are running high. The state department asking for up to 300 additional U.S. troops for unspecific security reasons in Baghdad.
The intelligence community worried what will happen next.
"It's not clear weather the leadership will now pivot towards attacking the West. There is certainly a lot of concern that they could. They have the capability to," Terrorism Expert Paul Cruickshank said.
The administration for now, not likely to significantly expand military action in Iraq.
Air strikes against ISIS inside Syria are unlikely given Syrian air defenses and the lack of intelligence about where ISIS operatives are located.
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