BAGHDAD - Eleven U.S. military personnel required medical treatment outside Iraq after Iranian missile strikes, defense officials said, reversing earlier assurances from President Donald Trump and the Pentagon that there had been no American casualties.

Eight of the service members are being assessed for concussion-like symptoms after the blasts, said Jonathan Hoffman, the chief Pentagon spokesman. Three others sought behavioral-health treatment to cope with the bombardment, in which ballistic missiles launched from Iran crashed into Al Asad air base west of Baghdad in waves Jan. 8, Hoffman said in an interview Friday.

Three of the service members left on a regularly scheduled flight to Camp Arifjan in Kuwait on Jan. 10, with the rest leaving Wednesday on a flight to Landstuhl Regional Medical Center in Germany, Hoffman said. The destinations were determined based on when their symptoms manifested themselves and when planes were scheduled, he said.

"They all walked onto the aircraft under their own power," Hoffman said. "These are people who were going to a doctor's appointment to get checked out."

The U.S. military first acknowledged the treatment in a statement Thursday night after a media report by Defense One. Navy Capt. Bill Urban, a spokesman with U.S. Central Command, said that "several were treated for concussion symptoms from the blast and are still being assessed."

"When deemed fit for duty, the service members are expected to return to Iraq following screening," Urban said. "The health and welfare of our personnel is a top priority and we will not discuss any individual's medical status."

The missile barrage last week against the sprawling air base in western Iraq left deep craters and the crumpled wreckage of living quarters and a helicopter launch site. At least two soldiers were thrown through the window of a tower that was about 15 feet high, U.S. military officials said in interviews.

The acknowledgment is a departure from initial reports from defense officials and the president, who described as inconsequential the effects of the missile salvos launched in retaliation for a U.S. drone strike that killed Iranian Maj. Gen. Qasem Soleimani in Baghdad.

"No Americans were harmed in last night's attack by the Iranian regime. We suffered no casualties. All of our soldiers are safe, and only minimal damage was sustained at our military bases," Trump said soon after the attack.

Hoffman said Friday that when the president spoke, his comments were based on "accurate, truthful information that he received" in the hours after the attack. Initial reporting from U.S. commanders in Iraq to the Pentagon said U.S. personnel suffered no loss of life, limb or eyesight, Hoffman said.

Information has continued to emerge since then. On Jan. 13, military officers at Al Asad told reporters that several service members were suffering from concussion-like symptoms.

But concussions are not always as immediately evident as shrapnel or gunshot wounds, and in the ensuing days, U.S. troops were assessed for blast injuries. The service members who left Iraq for treatment were sent for further care and screening "in an abundance of caution," Urban said.

Information about the service members who left Iraq for treatment Jan. 10 was slow in arriving at the Pentagon, reaching Defense Secretary Mark Esper on Wednesday after the second wave of patients left, Hoffman said.

That came on the heels of Esper describing damage to facilities and equipment in an interview Jan. 12 while offering fresh assurances that there had been "no casualties." Casualties are typically described by the U.S. military as personnel both wounded and killed.

The attacks came in waves for more than an hour and a half, with 11 missiles hitting the base, Esper has said. The air turned warm as light filled the night sky and shock waves ripped through the air, soldiers said in interviews, and the impacts sent door frames deeper into the ground.

In the aftermath of the attack, Army Lt. Col. Tim Garland said he had combed through the damage assessments with skepticism, thinking that it was impossible that no soldiers had been killed.

"We all know that the initial report is always somewhat inaccurate . . . I personally almost lost two of my soldiers," Garland told reporters at the base, describing how a blast some 50 yards from their position blew them out of a guard tower.

"How they survived that, I have no idea. It's an absolute miracle," he said. The base hosts about 2,000 troops, 1,500 of them from the U.S.-led coalition.

Commanders placed the base on lockdown at 11 p.m. on Jan. 8 after initial warnings of an impending attack. Then, before 1:30 a.m., a staff weather officer monitoring radar in the tactical operations center detected an imminent ballistic missile strike.

The troops scrambled in response. Nonessential personnel who were not already inside bunkers were told to run for cover, said Army Chief Warrant Officer Alex Bender. The staff weather officer closed the door behind him, Bender said, right before an explosion tore through the night.

"I'd just sent him to a bunker when the first round impacted," Bender said. "I thought: 'I've just killed him.' "

Inside the operations room, Bender lay beneath his desk as everything seemed to fall - pin boards, lamps, shards of glass.

The all-clear came shortly before sunrise, and as troops stepped into the open, they passed around cellphones so that people could inform their families that they were safe and that no one had been killed.

Although there was some speculation that the attacks were designed to avoid casualties, commanders at the base think that the strikes were intended to kill U.S. personnel.

- - -

Horton and Lamothe reported from Washington.

This article was written by Louisa Loveluck, Dan Lamothe and Alex Horton, reporters for The Washington Post. Horton reported from Washington.