Over the last 17 years, the Air Force has become very good at the fight against networks of violent extremists in the Middle East — a “machine” as Chief of Staff Gen. David Goldfein puts it.

“We are a machine because we’ve got this mature infrastructure (in place), and a mature campaign that already exists, and all the command and control is established,” Goldfein said Wednesday in Hawaii at the start of an Asia-Pacific trip.

But the emergence of China and Russia as “great power” competitors has forced a rethink of strategy with the Air Force embracing what’s known as multi-domain operations to mesh capabilities with other services across air, sea, land, cyber and space.

That means very different skill sets now have to be exercised, Goldfein said. Chinese missiles now threaten traditional bases, aircraft and ships from long distances.

Amid protests in Hong Kong, China has denied requests for port visits to Hong Kong by the USS Green Bay and USS Lake Erie, which were scheduled to arrive in the next few weeks, Cmdr. Nate Christensen, deputy spokesman for U.S. Pacific Fleet, said Wednesday.

Goldfein ticked off his requirements for expeditionary wing commanders to be sent to the Pacific, including the ability to establish remote bases and defend those outposts with integrated defenses.

“And as you defend that base you have to receive follow-on forces that don’t look like yours because they are (from another service) or they are allied,” Goldfein said.

Command and control will have to be set up on the fly, he said.

“You’ve got to be able to fight that base in an environment where you are likely to be cut off from portions of your network and you may be taking losses,” he said.

The Air Force’s top leader spoke to more than 1,500 airmen who spilled out an open hangar door at Joint Base Pearl Harbor-Hickam.

He also answered questions from airmen, including a query about a spike in suicides in the Air Force.

Goldfein and Gen. Charles Q. Brown Jr., the head of Pacific Air Forces, are traveling to Guam for a brief stop and then the Philippines, Vietnam and Australia.

Goldfein noted that he is the first Air Force chief of staff to visit Vietnam since the American war ended. The visit reflects broadening U.S. defense ties with the Southeast Asian nation as a possible counterweight to China.

Adm. Phil Davidson visited Vietnam for the first time in April as head of U.S. Indo-Pacific Command, saying the “U.S. relationship with Vietnam is one that continues to grow and certainly will be enduring.”

The Air Force chief told the airmen that multidomain operations call for a fusing of sensors and shooters across all services to rapidly respond in conflict using a wide variety of assets.

“I don’t necessarily want China or Russian leaders to be thinking that we are ever going to contemplate a linear battle with them,” Goldfein said.

Instead, with “what we have to throw at you, you will be looking up, down, left, right, forward, back — you have no idea what’s possibly coming at you,” he said.

He added that by providing “so many dilemmas from so many domains … maybe, just maybe, that’s what defines deterrence in the 21st century.”

Pacific Air Forces in April practiced rapid dispersal of aircraft, sending six F-22 fighters, two KC-135 refuelers and two C-17 cargo aircraft from Hickam, along with other aircraft, to Guam to exercise the ability to move them quickly to other islands.

The military has a long way to go with multidomain operations, however, including the need for all the services to agree on the same concept and develop joint doctrine for it.

Goldfein also talked about suicides in the Air Force, which have risen to 78 this year — 28 more than this time last year. The Air Force directed a one-day “resilience tactical pause” for leaders to engage with airmen on the issue.

“I actually don’t know right now what’s causing our increased numbers,” he said. “There’s no data that we’ve looked at that would indicate that we have something going on.”

Goldfein said the loss of life is a “call to arms” for the Air Force to address the problem, with ideas generated at the unit level likely to have the most success.