U.S. officials have consistently said the Daesh militant group is being degraded thanks to efforts by a U.S.-led coalition, but experts and statistics on the ground say otherwise Anadolu Agency reported
As of May, the U.S. has spent at least $2.4 billion on Daesh-related operations, or about $9 million daily, according to the Pentagon.
Deputy Secretary of State Antony Blinken told leaders gathered in Paris on Wednesday that the coalition has been successful against the militants as more than 10,000 Daesh members have been killed since the coalition began airstrikes in Iraq and Syria last August, and about 25 percent of the territory militants initially seized has been re-captured in nine months.
Those figures have failed to impress some. "I don't think that is a good return of investment," Lt. Col. Scott Mann told Anadolu Agency.
It is a lot of money spent for a relatively small number of achievements that are still view with a degree of skepticism because there are no troops on the ground to verify the claims being made, added Mann, who directors the Stability Institute think tank in Washington.
Coalition forces have conducted nearly 4,000 airstrikes against Daesh in Syria and Iraq, according to U.S. Central Command, but militants have succeeded in retaining the vast majority of territory it has captured and the group is coordinating offensives in those countries as well as others.
"Using the death of 10,000 ISIS [Daesh] members as a singular metric to gage your success -- that did not work in Vietnam, it has not worked in this 14 years of war [against al-Qaeda] -- will never work in fighting a group like ISIS," the retired veteran U.S. officer said.
The Pentagon said U.S. defense leadership does not track numbers to judge the success of operations against Daesh.
"What we are interested in capabilities, whether we have been able to degrade the enemy's capability to move, the enemy's capability to communicate, the enemy's capability to fund itself, the enemy's capability to supply itself," Pentagon spokesman Col. Steve Warren told reporters.
For all the achievements cited by the Pentagon, they are limited to rough estimates without any concrete findings.
Although 10,000 Daesh militants are estimated to have been killed, the Pentagon believes that the number of fighting militants remains somewhere between 20,000 and 32,000.
"As we kill ISIL [Daesh] fighters we know that ISIL continues to recruit," Warren said.
Noting the importance of working with the local population in dealing with Daesh, Mann said the U.S. has failed to work directly with the marginalized Sunni population to integrate them with Iraqi forces fighting the militant group.
"When we do these air campaigns and drones strikes on the areas where ISIS has embedded themselves within a tribal population, I think, we drive ISIS deeper into the population and we drive the population further away from us," he added.
Mann's claim is illustrated Thursday when a tribal council from Fallujah and al-Karma in Iraq's Anbar province declared allegiance to Daesh.
"If the local Sunni population in Ramadi are embracing ISIS and if ISIS is able to operate in Ramadi with impunity, then I don't care how many militants we have killed; we are still not effective," Mann said.
That position is supported by Daesh's recent capture of Ramadi - the capital of Anbar province - as well as a dam that supplies water to the city.
The terror group has also conducted several offensives in Syria that resulted in their control of various key areas including the ancient city of Palmyra with two gas fields and the Khunayfis phosphate mines 45 miles south of the city.
According to the Syrian Observatory for Human Rights, by May, Daesh had seized 95,000 square kilometers of land - nearly half of Syria's territory - as well as the last border crossing between Syria and Iraq that was held by the Syrian Army last week.
House Speaker John Boehner also expressed his concern about the advancement of the terror group saying that the U.S. is losing ground to Daesh in Iraq and Syria.
"Until there's an overarching strategy that involves not just us but our allies, we're seeing the growth of this problem growing much faster than our ability to slow it down," he said.