For 23 years, Christian Beyer worked around the concussive explosions of one of the most powerful weapons in the military – the M1 Abrams tank. And almost all that time he was an exemplary soldier, rewarded for his merits and promoted all the way to the rank of master sergeant in charge of training young tank crews.
Then in 2020, at the age of 38, he began to fall apart.
He couldn’t sleep. His family noticed that his balance was unstable and he began to slur his speech. He would cry over small things and think of imaginary conspiracies.
He became evil and then dangerous. One night in late 2021, according to military documents, he shoved his wife during an argument and then grabbed a kitchen knife when a senior sergeant tried to calm him down.
As Sergeant Beyer’s struggles began, the military was just beginning to realize that heavy weapons fire can cause brain damage. Mandated by Congress, it began setting up programs to monitor and limit exposure, published its first safety threshold for the intensity of an explosion to avoid “adverse brain health outcomes”, and compiled a list of 14 weapons it can pose a significant risk.
But the M1 Abrams was not on the list. Tests of the tank’s 4,000-pound main gun revealed it was well below the new safety threshold. So the Army continued to treat him as safe, and Sergeant Breyer continued to work.
However, the threshold is less scientific than it seems. It’s not a measure of brain health risk based on rigorous research, but a decades-old guideline of how likely blasts are to burst a soldier’s eardrums, borrowed on short notice because the Pentagon had nothing better to do. Explosion researchers say it may not provide a reliable gauge.
“It’s basically a placeholder, because nobody knows what the right number should be,” said Christian Franck, a professor of biomechanics at the University of Wisconsin-Madison who is part of a team modeling the effects of blasts on the brain for the Department of Defense. He repeated the assessment of many other researchers.
“If the right kind of wave hits the brain tissue, the tissue just breaks — literally disintegrates,” said Dr. Frank. “We see that in the laboratory. But what kind of explosion will do that in real life? It’s complex. Work takes time. There’s a lot we don’t know.”
The vast majority of explosions occur in training, not in combat, and instructors are often exposed far more than anyone else. But unlike troops on a combat deployment, instructors are not screened for brain injuries.
As Sergeant Beyer’s condition worsened, his wife, Christy Beyer, said she became concerned that he had been exposed to too many tank blasts and told his command that he needed a thorough medical evaluation.
The army decided he needed something else: punishment.
Instead of sending him to one of the military specialized centers for brain injuries to determine whether a brain injury or some other factor could have caused his deterioration, his commanders court-martialed him for pushing his wife and other crimes related to the incident. It is still unclear whether his change in behavior is due to the brain injury. The military jailed him, reduced his rank, and then forced him to retire this spring.
“Something changed in his brain,” Christy Beyer said recently in an emotional interview, often pausing to cry. “I begged people, his command, the police to help him, but nobody did.”
Out of uniform, Mr. Beyer continued to spiral out of control. He left his wife and three children and wandered the country without any direction. In October, police say, he pulled a knife on two gray-haired men in Northern California during a parking dispute, tried to run them over with his car, then fled, plowing through vineyards, crossing a river and embarking on a days-long manhunt.
The decorated former master sergeant is now in jail, awaiting trial on state and federal criminal charges. He pleaded not guilty. Mr. Beyer could not be reached for comment and his lawyer declined to comment.
The Department of Defense’s new explosion safety threshold measures the force of an explosion based on the peak pressure of the blast wave: anything over four pounds per square inch is considered potentially harmful.
But peak pressure is only one measurement, and blast waves are complicated, says Dr. Franck, explosion researcher. Some waves reach a high peak but pass quickly, while others with lower peaks may last longer and deliver more energy.
While much about how blasts damage the brain remains unknown, the military has been studying their effects on the lungs and ears for decades, and in those studies some waves with lower peaks “may actually be more insulting to the human body,” said Timothy Kluchinsky, an Army researcher who studies gun safety.
He agreed that the current safety threshold may not be the best way to assess the risk of an explosion. But he said the department needs to establish some kind of metric that would alert the armed services to treat weapons explosions with caution.
The existing eardrum threshold was, Mr. Kluchinsky said, “the easiest thing for the user community to understand.”
Almost all weapons from the list of 14 potentially dangerous weapons of the Ministry of Defense have measured below safety threshold. But the troops who shot them did reported several times concussion-like symptoms.
The Army started an effort called the Warfighter Brain Health Initiative to coordinate research, safety guidelines and blast exposure monitoring, but it’s still ongoing, and it was started quickly before it was finished, says Kathy Lee, the initiative’s director.
“We have to offer solutions,” Ms. Lee said in an interview. “If we can get to an 80 percent solution and get it out there, it might not be perfect, but we can develop properly.”
She said the safety threshold is part of a comprehensive new approach, including a program that will regularly test all soldiers for brain injuries starting next year.
Few people would dispute that the M1 Abrams tank delivers a punishing blast. Soldiers are required to wear double ear protection if within 800 feet and must remain at least 30 feet behind the tank when it fires.
The tank is designed to be sealed during firing to protect the crew inside, but in practice crews regularly keep the top hatches open. This allows the blast to reverberate through their compartment, where the military says it peaks at about two pounds per square inch. The boom they hear has been measured at 172 decibels – more than 100 times louder than the sound of a jet engine.
“It’s pretty violent,” said Daniel Gade, a retired Army lieutenant colonel who commanded a tank company in Iraq. “I don’t think there’s a guy who’s shot that doesn’t think it’s taking a toll.”
Army spokesman Lt. Col. Robert Lodewick said all available data suggested the risk to the tanks from exposure to the blast was “low.” In more than 20 years, he said, the military has not recorded any brain injuries associated with firing the Abrams gun.
Blast research is evolving, Col. Lodewick said, adding that “the Army remains committed to understanding, mitigating, accurately diagnosing and rapidly treating blast overpressure and its effects in all its forms.”
This can be difficult, however, because brain injury symptoms can take years to develop and can include depression, anger, mood swings and other problems that are often mistaken for unrelated mental health conditions.
Artillery soldiers exposed to thousands of M777 howitzer blasts and eventually diagnosed with brain injuries told The New York Times that they were initially misdiagnosed with psychiatric problems or punished for misconduct.
Mr. Beyer joined the Army right out of high school and had an unusually long career spent entirely around tanks, including six overseas deployments, three of them to Iraq. His last assignment was as a tank instructor at one of the Army’s busiest training sites, Fort Irwin in California.
A typical tank crew fires about 120 rounds a year and works around tanks for only a few years before leaving the military or moving on to other assignments. Mr. Beyer never moved on.
A Fort Irwin spokesman said that while most of the training was done with lasers instead of live rounds, a typical tank instructor would be exposed to 120 to 240 rounds a year. Other tanks estimated that Mr. Beyer could easily have experienced more than 3,000 explosions in his career.
He was also hit by a roadside bomb in 2008, which left him temporarily dazed.
Research suggests that while single blasts may not cause immediate, obvious injury, undetected damage can accumulate over repeated exposure, causing neural connections to eventually fail.
For decades, the military has noticed that an unusual number of soldiers reaching middle age exhibit behavioral problems – a phenomenon it once called “old soldier syndrome.” In recent years, some researchers have suggested connection with exposure to the explosion.
The 40-year-old reservist named Robert Card, who killed 18 people in a shooting in Maine in October, had worked as a grenade instructor for years. His brain is being tested for damage.
Mr. Beyer’s troubles began slowly, his wife said. His hearing got worse every year. As a young soldier, he loved watching “Danger!” and he shouted out the answers before the contestants did, but as time went on his memory became so spotty that he often had trouble finding his keys.
The decline increased even more after he arrived at Fort Irwin in 2020. He complained of sharp pain in his ears, and his heart would sometimes beat as if he had run a mile, even if he was sitting on the couch. His digestion was so painful that he would lie in the tub and cry. Brain injuries can cause cardiac and intestinal dysfunction.
He started drinking. At first his wife blamed alcohol for his deterioration. However, after he was arrested for a pushing incident in 2021, he stopped drinking.
“He was sober, but he still didn’t make sense,” she said. “He would talk about the voices in his head. Something is clearly wrong with him.”
dr. James P. Kelly, who for years led the military’s brain injury treatment program and now leads it brain injury clinic at the University of Colorado, said breakdowns in soldiers with multiple combat deployments can have many causes, including post-traumatic stress disorder or mental illness unrelated to military service.
Even so, said dr. Kelly, there are tests that can detect evidence of brain injury, and “given this guy’s military blast exposure, that would certainly be my first thought.” He added: “It is absolutely critical to carry out a thorough assessment.”
Christy Beyer said no such assessment has ever been done. After her husband was court-martialed last year, she said, he became paranoid and angry, convinced the military was out to get him.
Days after becoming a civilian, he abandoned his family without explanation, convinced his wife was part of an imaginary plot against him, Ms. Beyer said.
In October, at his old military post, he published a riotous rant threatening to kill certain people. After a knife incident in Northern California, the police tracked him down and arrested him at his father’s home in Petaluma, California, and federal prosecutors charged him in November with interstate threats. He also faces local charges in California.
His family had hoped he could be released from prison and committed to a psychiatric hospital, but a federal judge denied him bail. Mr. Beyer is being held at a federal detention center in Los Angeles and could face years in prison.
Mrs. Bejer is worried that the civilian authorities, like the military, will never take into account the damage that could have been done by so many tank explosions.
“I know in my heart and soul that this is an injury of war,” she said. “I just wish someone would see it.”