Jim Michaels

USA TODAY

The U.S.-led coalition has increased the number of bombs dropped on the Islamic State by about 50% this year, reflecting the progress U.S.-backed ground forces have had in pushing militants out of key strongholds in Iraq and Syria.

A total of 14,192 rockets, bombs and other munitions were dropped in the first four months of this year, up from 9,442 during the same period in 2016, according to the latest monthly statistics from U.S. Air Forces Central Command.

The expansion of airstrikes "can be attributed to the increased pace of operations in both Iraq and Syria as we target and destroy ISIS," Lt. Col. Damien Pickart, a spokesman for Air Forces Central Command, said Tuesday, using an acronym for the Islamic State.

U.S.-backed ground forces are engaged in offensives against militants in Mosul, Iraq’s second-largest city, and in Raqqa, the terror group’s de facto capital in Syria.

The increase comes as President Trump has given battlefield commanders more authority to approve airstrikes and raids, which has quickened response times. “He delegated authority to the right level to aggressively and in a timely manner move against enemy vulnerabilities,” Defense Secretary Jim Mattis said last week.

Under former president Barack Obama, many of those decisions were reserved for the military's highest levels.

Air Force officials say they have not loosened the rigorous standards for approving airstrikes despite the uptick in activity. Pickart said about 90% of the munitions used have been precision guided. "The protection of civilians remains a cornerstone of the campaign," he said.

The U.S. military has also expanded the number of special operations advisers in Iraq and Syria, which has helped coordinate the strikes with local forces, said Chris Harmer, an analyst at the Institute for the Study of War.

The Pentagon has about 1,000 U.S. troops in Syria and about 5,000 in Iraq, which includes hundreds of advisers working with local ground forces.

Trump has also ordered the Pentagon to shift tactics to surround militants and prevent them from escaping at the last minute. In the past, militants were often able to flee as U.S.-backed ground forces closed in on their positions.

“We carry out the annihilation campaign so we don't simply transplant this problem from one location to another,” Mattis said.

In Raqqa, U.S.-backed forces have cut off most ways out of the city and are preparing for a final assault into the city.

Read more:

Defense Secretary Jim Mattis says President Trump's orders will annihilate ISIS

Vice President Pence says ISIS is waging anti-Christian 'genocide'