One day, he had to choose which of two groups of soldiers would travel with the only available explosives-clearing team. The group he sent out with the team had no trouble. The group he sent out alone hit a roadside bomb.
Three soldiers died. Cantwell wanted to vomit.
The violence left him in despair. He was visiting a neighborhood when a car bomb exploded. Cantwell stared at brain matter and blood sprayed across a wall. Two tiny pink sandals lay on the ground below the stain. One floated in a pool of blood, the wind turning it in a circle.
Cantwell knew the dead child's sandals would join the hand in his nightmares.
He grew bitter and disillusioned. The job left little time for sleep. When he did, the nightmares were grislier than ever.
An officer asked one morning if he was OK. Cantwell assured him: "I'm fine."
He wasn't. But before he left Baghdad, he was promoted to major general and appointed Deputy Chief of the Australian Army.
Jane was stricken by her husband's appearance when he returned home. He was exhausted and sick.
The guilt of the soldiers' deaths from the roadside bomb was eating at him. Jane tried to assure him he was not responsible. He ignored her. In his mind, it would always be his fault.
He quietly visited another psychiatrist who put him on medication. It did little to help.
The pressure of pretending was almost unbearable.
Cantwell stared at the two flag-draped caskets before him. Inside lay the first Australians to die in Afghanistan since Cantwell had taken command of Australia's forces in the Middle East.
They had been his responsibility. Now they were dead, torn apart in an explosion.
At their memorial, he spoke of bravery and sacrifice. Many in the audience cried. He strangled his own misery into silence.
After the service, he climbed on board the plane bound for the morgue and sat next to the caskets, thinking about the men inside. His warrior self tried to reject the nagging feeling that they had died because of him. He tried to think rationally: He had done his best.
But the line between his two selves was disintegrating. He began to cry. A friend on board asked if he was OK.
Cantwell could not answer.
He wondered if all the bloodshed was worth it.
He was at the beach on vacation with Jane. But he was detached from everyone and everything.
There were rumors he was up for a promotion to Chief of the Army when he was summoned to the nation's capital to give his debrief on Afghanistan.
He donned the warrior mask one last time. He appeared calm, made jokes.
When it was over, his superior asked him how he was really doing.
Cantwell surrendered. He said: I am not OK. I am not sleeping. I am not who you think I am. Please tell the chief of the defense force.
Cantwell told the chief himself that he could not take the job. The chief understood.
His truth exposed, Cantwell hoped the worst was over. It was not. On a train, he was so startled by the conductor calling out for tickets that he shouted in terror. The other passengers laughed. He cried.
A psychiatrist finally asked: Had he thought of suicide?
He answered: Yes.
The pressure that had been building for 20 years was at bursting point.
Cantwell let go.
A pajama-clad woman in the psychiatric ward asked the general why he was there.
He wondered, too.
He had checked himself into this hospital, knowing he was broken. Still, he argued with himself: What is a major general doing here?
The doctors changed his medication, and he attended regular counseling sessions. One night, he only had one horrible dream — an improvement.
He left after a week of intense treatment. A few months later, he retired. He and Jane moved to a peaceful coastal community, where he continues his therapy.
He doesn't regret his career. Australia's Defense Chief Gen. David Hurley said Cantwell's courageous decision to go public has already encouraged other members of the military to come forward with their own struggles.
But speaking out isn't easy. Military personnel often fear the stigma of mental illness will ruin their careers, and they worry that people will think they are not fit to lead, says Matthew Friedman, executive director of the U.S. Department of Veteran's Affairs National Center for PTSD.
To Cantwell, soldiers are simply not conditioned to expose their pain.
"We've instilled in them this idea of physical and mental toughness — that's how they win battle, that's how we win wars," Cantwell says. "We expect that same person with the self-image of a warrior — someone who is tough and imperturbable and able to shrug off pain and difficult environments and horror and get on with their job — suddenly we expect them to turn around and open up? It just doesn't work."
He sits at his computer and reaches for the mouse. There is a click as a button attached to the bracelet he wears hits the table. He wove it out of parachute cord as a reminder of the 10 men who died under his command in Afghanistan.
He insists the bracelet is not a punishment but a mark of respect.
Maybe it is both.
How are you feeling today, John?
His answer is now honest: Not good.
His sleep has been tormented by the usual nightmares. Upon waking, he sees the headline that another Australian soldier has died in Afghanistan.
His stomach drops. He knows these feelings may never go away. He hopes he can eventually forgive himself for the men who died under his command. But he never wants to forget.
"One day I'm hoping to be able to touch on these emotions, experience them and yet not let them get their hooks into me," he says. "That'll come one day. One day."
Until then, he will focus on rebuilding himself — his real self. He wants to learn to sail and scuba dive. He wants to write and paint and draw ("something a bit creative rather than destructive," he says with a chuckle.) Maybe he'll work with veterans, or become a mental health advocate.
Not long ago, he turned 56. He wanted to celebrate with a trip to the beach, but driving a car brings flashbacks of car bombers in Iraq. So he and Jane hopped on his motorcycle and roared down the road. At a surf club, they grabbed seats on the deck. The general clutched a cold beer.
"Life is pretty good," he thought, watching the waves roll in. "Despite everything — life is pretty good."