Carolyn Kaster/AP
The troops headed to the war-torn country - presumably several thousand of them - will join the roughly 12,000 already on the ground. But the total number is yet to be announced.
"It's more advisers. It's more enablers - fire support, for example - and then some other things," Mattis said on Thursday. "I'm not going to give you the details right now until I talk to the Congress."
With the reinvigorated effort, the Air Force - already facing its own strains - may also see expanded involvement in America's longest war.
What that involvement will look like and require, however, remains uncertain, Air Force Chief of Staff Gen. David Goldfein and Air Force Secretary Heather Wilson told Reuters.
Goldfein said the branch was "absolutely" reviewing potentially increasing its presence in the wake of Trump's decision. "It's actually too early to tell what this will mean in terms of plus-ups and reductions," he said.
(US Air Force photo by Senior Airman Jordan Castelan)
Trump's August 21 speech announcing the new policy emphasized greater commitment - both political and material - to "killing terrorists." Goldfein and Wilson said the president's remarks indicated more support for striking insurgents in Afghanistan.
"Obviously the Joint Chiefs will work through their plans and make proposals, but I think the guidance was pretty clear from the president last night, and we're going to go on the offensive and destroy these terrorist networks," Wilson told Reuters.
US bases around the Middle East have been supporting the campaign against Taliban and ISIS militants in Afghanistan, and the number of US Air Force personnel on the ground there is relatively small compared to the scope of the US commitment to the war in Afghanistan.
(U.S. Air Force photo/Senior Airman Justyn M. Freeman)
Goldfein told Air Force Times that military planners were already evaluating how to implement Trump's new approach, but the exact details are yet to be decided.
"For me, this is about how do we optimize the air-ground team to accomplish the stated objectives. That's the key. It's not just, 'I need six more of these or five more of these.'" Goldfein told Air Force Times.
"It's actually, 'OK, here are the objectives, here is what the footprint needs to look like on the ground in order to optimize the footprint that we place in the air,'" he added.
That optimization may mean changing the way ground troops, including those from the Air Force, work with aircraft providing intelligence, surveillance, and reconnaissance, as well as with the personnel who analyze the information that is gathered. The Air Force also provides close-air support, personnel recovery, airlift, and aerial refueling support in Afghanistan.
Trump's assertion that he will expand the ability of the US military to strike "terrorist and criminal networks" in Afghanistan may mean loosening the rules of engagement to allow more Air Force strikes there.
Goldfein told Air Force Times that Lt. Gen. Jeffrey Harrigian, commander of US Air Forces Central Command, and Maj. Gen. James Hecker, the top Air Force officer in Afghanistan, would request any additional resources, and, once they have them, "they'll be the ones that will be driving this new way of doing business."
US Air Force photo by Capt. Eydie Sakura/released
The Air Force chief of staff said it was hard to predict how the branch's footprint in Afghanistan would change, as operational needs may shift in the future.
While increased targeting of Taliban and ISIS forces would likely require more Air Force assets to build intelligence, launch strikes, and support allied forces, Air Force resources needed in Afghanistan could also decrease, based on US military assessments, Goldfein said.
The Afghan air force is made up of a small contingent of A-29 Super Tucano turboprop light-attack aircraft (it will have 20 by the end of 2018), and Wilson said the Air Force would look to assist the Afghan government with acquisitions if it requested more A-29s. (The US is considering buying its own light-attack force and may send some to the Middle East for combat demonstrations in the future.)
But those planes likely can't fill the role of US fighter jets, John Venable, a Heritage Foundation fellow and former pilot, told Air Force Times, meaning there will be a continued need for US aircraft to provide tactical support.
But that continued support may only mean the deployment of a squadron-size contingent of aircraft like F-15s, F-16s, or A-10s to bolster the aircraft already in Afghanistan, Venable said.
US Air Force photo/Tech. Sgt. Nicholas Rau
Though victories against ISIS in Iraq and Syria may make more resources available for Afghanistan, Trump's change in policy comes as the Air Force grapples with a number of protracted operational commitments.
US F-16s have led the three-year air war against ISIS in Iraq and Syria, flying 15% of the sorties. The A-10 has flown 14% of US sorties and dropping 19.3% of the total weapons used. US F-15s have carried out a similar number of strikes and dropped nearly as many weapons as the A-10s. Aircraft from other coalition forces have conducted a combined 14% of strike missions, the US said.
Outside of those combat operations, US Air Force aircraft and personnel are spread across Europe as part of the US's NATO commitments.
Thomson Reuters
Seven F-15C Eagles and 140 airmen recently deployed to Lithuania to take over an air-policing mission through the end of the year.
Six F-15C Eagles and about 280 support airmen also recently arrived in Iceland for a training and air-surveillance mission in support of NATO. Three US bombers are also in Eastern Europe for a few weeks of demonstrations and exercises.
US Air Force aircraft in Japan and South Korea have also taken part in numerous shows of force and exercises in recent months, amid ongoing tensions with North Korea.
The Air Force is also facing administrative challenges - an ongoing pilot shortage, in particular. The branch has boosted pay, increased bonuses, changed training requirements, and called for retired pilots to return - all to entice fliers to stay in uniform and to be able to meet mission needs.
The Air Force has appointed Brig. Gen. Mike Koscheski to lead its aircrew crisis task force, formed earlier this year. He's the first general office to helm the task force and "will be focused ... on retaining and growing pilots in order to address the shortfall," Wilson said.