Secretary of War Pete Hegseth said on March 2 that four U.S. service members were killed during the Iran conflict after an Iranian projectile—which he referred to as a “squirter”—penetrated American air defenses and struck a U.S. tactical operations center.

Hegseth emphasized that while air defense systems are highly capable, they are not flawless.

“As it pertains to the U.S. casualties, that particular incident was, you know, you have air defenses and a lot’s coming in, and you hit most of it. And we absolutely do. We have incredible air defenders,” he said.

Hegseth noted that despite the center’s fortifications, the weapon involved was powerful.

He added that such incidents strengthen the military’s resolve.

On Sunday, U.S. Central Command announced that three American service members were killed and five others seriously wounded during U.S. strikes on Iran, marking the first American fatalities in the operation, known as Operation Epic Fury.

The command also reported that several others suffered minor shrapnel wounds and concussions and are expected to return to duty.

On Monday, Central Command confirmed that a fourth soldier had died from injuries sustained in the attack.

Joint Chiefs Chairman Gen. Dan Caine said on Monday that more U.S. casualties are expected.

“We expect to take additional losses, and as always, we will work to minimize U.S. losses,” he said. “But, as the secretary said, this is major combat operations.”

President Donald Trump expressed condolences in a video posted on Sunday on his Truth Social platform.

“We pray for the full recovery of the wounded and send our immense love and eternal gratitude to the families of the fallen,” Trump said.

In the six-minute video, Trump described the fallen troops as “true American patriots who have made the ultimate sacrifice for our nation.”

He said the United States would avenge their deaths.

Trump told The Daily Mail that he believes the conflict could last “four weeks or so.”

Hegseth declined to give a timeline and said that Trump will determine how long the operation will last.

The secretary also did not rule out U.S. boots on the ground, though he said there are currently none in Iran.

“We’re not going to go into the exercise of what we will or will not do,” he said.

“And so President Trump ensures that our enemies understand we'll go as far as we need to go to advance American interests.”

Caine said that more forces are heading toward the Middle East.

Navy Adm. Brad Cooper, the head of Central Command, “will receive additional forces even today,” he said.

“This rapid buildup of forces demonstrated the Joint Forces’ ability to adapt and project power at the time and place of our nation’s choosing,” he said.

In response to a question from The Epoch Times, Caine confirmed that additional tactical aircraft are entering the theater and said U.S. forces are “just about where we want to be in terms of total combat capacity and total combat power.”

Hegseth said that the U.S. military operations in Iran are not another Iraq.

“This is not endless. I was there for both. Our generation knows better, and so does this president,” he said. “He called the last 20 years of nation-building wars dumb. And he’s right. This is the opposite.”