Nowhere has the shift been more visible than in the fight against the ISIS group in northern Syria, where under Barack Obama even minor tweaks to US plans underwent exhaustive White House scrutiny.
Since Trump's inauguration, the Marine Corps has brought an artillery battery into Syria, and the Army has flowed in hundreds of Rangers, bringing the total number of US forces there to almost 1,000.
Commanders are weighing the possibility of deploying hundreds more, and the Pentagon this week announced it had provided artillery support and choppered local forces behind enemy lines in a bid to seize a strategic dam.
The greater leeway marks a departure for the National Security Council (NSC), which coordinates foreign and military policy and implements the president's national security agenda.
Under Obama, the NSC oversaw just about every aspect of America's wars in Iraq, Syria and Afghanistan, with then Pentagon chief Ash Carter was kept on a short leash.
Trump, conversely, has repeatedly deferred to his defense secretary, Jim Mattis, on military moves.
Mattis, a retired general, has delegated expanded authorities to his battlefield commanders.
"Jim Mattis has been given the latitude to conduct military operations in the way he sees best," Pentagon spokesman Chris Sherwood said.
'30-something year olds'
The United States is fighting ISIS in Iraq and Syria and the Taliban in Afghanistan "by, with and through" local forces backed by US and allied air power.
That overall strategy hasn't changed, but commanders now have greater discretion to move troops and equipment around.
Troop increases were especially sensitive for Obama, who campaigned on a promise to end America's Middle East wars and not put US boots on the ground.
Senator John McCain, who heads the Senate Armed Services Committee, was a frequent critic of what he calls NSC micromanagement. The veteran lawmaker said he favors battlefield commanders getting greater latitude.
"We don't have to ask the 30-something-year-olds for permission to respond to an attack in Afghanistan," he said.
McCain's congressional counterpart Mac Thornberry described a visit he made to Afghanistan under Obama, when he overheard a call from an NSC staffer asking how much fuel was in the planes on the tarmac.
"The level of micromanagement was incredible, and of course by the time you work your way through the NSC process your target has moved," he said.