Around 8 p.m. in the evening of January 7, 2020, United States Army Major Alan Johnson looked tearfully into a cellphone camera and began recording a farewell message he hoped his wife and son would never have to watch.
"I need you to be strong, okay?" Johnson said. "For mom. And just always know in your heart that I love you. Okay, bye buddy."
Maj. Johnson, a flight surgeon, who first enlisted in the United States military in 1991, was informed by a U.S. military intelligence officer that Iran was fueling medium-range ballistic missiles to destroy Al Asad Airbase in Iraq. Johnson and nearly 2,000 other service men and women were stationed at the base.
The attack was in retaliation for a U.S. drone strike that killed Iranian General Qasem Soleimani.
Hours later, 11 theatre ballistic missiles with warheads weighing more than 1,000 pounds each began raining down on the U.S. base and the surrounding area. It was the largest ballistic missile attack against Americans in history.
"Words can't even describe the amount of energy that is released by these missiles," Maj. Johnson told 60 Minutes. "[It] knocked the wind out of me, [I] immediately lost all my hearing, [I] felt like I was underwater…followed by the most putrid tasting ammonia…dust that swept through the bunker [and] coated your teeth."
Maj. Johnson told 60 Minutes contributor and CBS News national security correspondent David Martin that he survived the bombing in a bunker that was originally constructed to withstand 60-pound munitions.
Army Major Robert Hales, the highest-ranking medical doctor on the base, told 60 Minutes the attack was "sci-fi movie-like." During the bombing, he was in an armored vehicle a safe distance outside the base and feared he would return to find hundreds of his fellow troops dead.
"I honestly thought that I was going to come back, once the attack was over, and see just mass casualties across the base," Hales told Martin.
No U.S. troops were killed during the attack, but within days it became clear that it was a mass casualty event. More than 100 service men and women were diagnosed with traumatic brain injuries caused by concussions sustained during the bombing.
Maj. Hales told 60 Minutes there is not a lot known about brain trauma caused by a ballistic missile attack of this magnitude, in part due to its unprecedented nature.
"There hasn't been a lot of studies with this level of percussion wave, with the overpressure and the negative pressure that immediately follows being exposed to this, over and over again," Hales said of the Iranian missile attack. "Just because this missile attack was so unique as it never has happened in history that a ground force was exposed to 11 theatre ballistic missiles."
More than a year later, the side effects from the blast still linger for some of the troops who were stationed at Al Asad the day it was attacked.
Multiple soldiers stationed on the base told 60 Minutes about the headaches they still experience, including Maj. Alan Johnson.
Johnson was evacuated from Iraq to a medical center in Germany where he underwent physical and speech therapy. He reports that he still suffers from daily headaches, ringing in the ears, and post-traumatic stress disorder. Major Alan Johnson was awarded a purple heart for his injuries.
The video above was produced by Keith Zubrow and Sarah Shafer Prediger. It was edited by Sarah Shafer Prediger.