The President declared he would no longer announce troop levels but would focus on allowing US forces to target the Taliban and other terrorist groups wherever they were in Afghanistan.
The President is giving the Pentagon authority to ramp up troop levels in Afghanistan by several thousand, but Trump declared the US military would not talk specifically about troop levels there.
"We will not talk about numbers of troops or our plans for further military activities," Trump said. "Conditions on the ground, not arbitrary timetables, will guide our strategy from now on. America's enemies must never know our plans or believe they can wait us out."
The US currently has about 8,400 troops in Afghanistan, and US military generals have said that a few thousand more troops would help the US break the current stalemate against the Taliban.
The additional troops would serve in two roles: counterterrorism missions and training the Afghan forces.
Trump referenced both on Monday, talking about seeking out terrorists wherever they were and saying the US was committed to working with the Afghan government, while noting that the US support "is not a blank check."
More military autonomy
Perhaps the biggest military change Trump announced Monday was to relax US authorities to attack the Taliban and other terrorist groups in Afghanistan.
The Obama administration placed restrictions on US offensive operations in Afghanistan after the Afghan forces took the lead on fighting the Taliban, a move that frequently frustrated commanders in the field.
"Micromanagement from Washington, DC, does not win battles," Trump said.
He added that he would give military commanders the authority to act in real time and expand the authorities for US armed forces to target terrorists and criminal networks in Afghanistan.
"These killers need to know they have nowhere to hide, that no place is beyond the reach of American might and American arms," Trump said. "Retribution will be fast and powerful."
The end-goal of Trump's plan in Afghanistan was to bring the Taliban to the negotiating table to find a political solution to the Afghan war.
The goal was the same as that of President Barack Obama, but Trump argued his plan has a key difference from that of his predecessor: no timelines on the withdrawal of US troops.
"I've said it many times how counterproductive it is for the United States to announce the dates we intend to begin or end military operations," Trump said.
His criticism is one that Republicans frequently raised during the Obama administration, as Obama withdrew troops down to the current level of approximately 8,400.
While Trump talked about a political solution, he also expressed skepticism the Taliban would come to the negotiating table.
"Someday after an effective military effort, perhaps it will be possible to have a political settlement that includes elements of the Taliban in Afghanistan, but nobody knows if or when that will ever happen," Trump said.
Trump echoed comments from his predecessors in their desire to get Pakistan to change its terrorist-harboring ways.
Pakistan's role in providing a safe haven for the Haqqani network has frequently been a thorn in the side of the US military.
Trump threatened to cut off US aid to Pakistan to persuade them to help fight terrorism in Afghanistan.
"We have been paying Pakistan billions and billions of dollars at the same time they are housing the very terrorists we are fighting," Trump said. "But that will have to change, and that will change immediately."
Trump also talked about how India, a nuclear rival of Pakistan, could contribute to the Afghan war effort. He noted the billions of dollars in trade between India and the US and said his administration wanted India to help more on Afghanistan, particularly with economic assistance and development.
Winning ... but not nation-building
When Obama talked about the war in Afghanistan, he focused on bringing US troops home. Trump made clear he wants victory there.
"Our troops will fight to win. We will fight to win," Trump said. "From now on, victory will have a clear definition, attacking our enemies, obliterating ISIS, crushing al Qaeda, preventing the Taliban from taking over Afghanistan and stopping mass terror attacks against America before they emerge."
But the key thing Trump made clear to move away from — a nod to the isolationist wing of his supporters who backed a US pullout from Afghanistan — was nation-building.
"We want them to succeed, but we will no longer use American military might to construct democracies in far-away lands or try to rebuild other countries in our own image," Trump said. "Those days are now over."
Trump said bluntly that the US was "not nation-building again."
To finish the point, he added: "We are killing terrorists."