Trump says US cities should be military training grounds
The president repeated his criticism of Democratic-led cities including San Francisco, Chicago, New York and Los Angeles and indicated he would continue his policy of using military for law enforcement.
"They're very unsafe places and we're going to straighten them out one by one," he said, adding that it would be a "a major part for some of the people in this room".
"It's a war from within. Controlling the physical territory of our borders is essential for national security. We can't let these people in," he added.
Illinois Governor JB Pritzker accused Trump of using military troops and Immigration and Customs Enforcement (ICE) to "invade and disrupt" US cities.
"Our troops and our nation deserve better than you acting as a petty tyrant," he said in a post on X.
Security was extremely tight for the address at Marine Corps Base Quantico, a sprawling 55,000-acre facility in Virginia. The summit represented a rare gathering of so many senior personnel in one place.
Generals and admirals stationed around the world listened silently to the two men's remarks.
The event began with an address from Hegseth, who announced that the US military will require combatants to meet the "highest male standard" in physical fitness tests.
Hegseth acknowledged that the move may exclude some women from serving.
"Standards must be uniform, gender neutral, and high," Hegseth told the crowd.
Hegseth outlined his visions for cultural shift at the Pentagon and a greater "warrior ethos". He was echoed by Trump, who spoke afterwards.
His speech focused on the culture of the US military, training, leadership, and "fixing decades of decay", including DEI (diversity, equity and inclusion) programmes and the promotion of a "risk-averse" officer corps.
He said those officers had been unnerved by "climate change distractions", "woke garbage" and fears of being labelled as "toxic" leaders.
As well as announcing changes to fitness standards, Hegseth vowed an end to the "era of unprofessional appearances" - including beard exemptions - and to anonymous complaints procedures, as part of wider departmental changes.
Illinois Senator Tammy Duckworth, a military veteran, told the BBC she was worried about what Hegseth's remarks would mean for the future of the US military.
"His comments today are going to affect all kinds of recruiting, not just women, I don't know folks who want to serve in a military that's being used for political theatre," she said.
Duckworth said Hegseth was trying to get women and people of colour out of the military.
"For a guy who's not qualified for his own job, it's pretty discriminatory to talk about women who are qualified to do their jobs," she said.
Hegseth also addressed his previous firing of senior commanders, saying that he went with "his gut" and rid the military of those he believed would not shift away from policies set in previous administrations.
"More leadership changes will be made, I'm certain," he said.
No official reason was publicly provided when the generals were summoned at short notice last week, prompting a flurry of speculation around what Trump and Hegseth would say.
Speaking about Hegseth's reforms, Trump said that a focus on "fitness, ability and character" is not to "protect anyone's feelings".
"It's to protect our country. We will not be politically correct when it comes to defending American freedom," he said.
The president also applauded his move to rebrand the Defence Department as the Department of War.
He said the secondary title for the Pentagon was "so popular", even among his detractors, and contributed to what he has repeatedly claimed are skyrocketing recruitment figures.
"It's a historic re-assertion of our purpose, our identity and our pride," he said.