Intelligence sources previously told NBC News that the operation to take out al-Shishani — nicknamed Omar the Chechen, known for his red-tinged beard — occurred near the town of Shaddadi, which was seized by Syrian rebels from ISIS last month and was part of a campaign to retake ISIS-held territory.
The State Department had put a bounty of up to $7 million for Iraqi-born al-Qaduli, who officials said had reintegrated himself into ISIS in Syria following his release from prison in 2012. He had also ascended the ranks of al Qaeda after joining in 2004, and was under the command of leader Abu Musab al-Zarqaei, who was killed in 2006.
Al-Qaduli was previously reported to have been killed last year during an airstrike on a mosque.
According to reports, he is a former Iraqi physics teacher who had emerged as ISIS' temporary leader and No. 2 after al-Baghdadi was supposedly wounded in coalition bombing.
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Carter said beating back ISIS will continue to take time, but that the coalition is "gathering momentum, and we're seeing that momentum is having effect."
"We've learned a great deal," he added, "and we're continuing to learn how they get their finances and dry them up."
Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, told reporters during the news conference that ways to increase U.S. support for the ground fight in Iraq against ISIS will be on the agenda with President Barack Obama.
"The secretary and I both believe that there will be an increase in U.S. forces in Iraq in coming weeks, but that decision hasn't been made," Dunford said.