Brennan, a retired USMC sergeant, suffered a traumatic brain injury while serving in Afghanistan. In Shooting Ghosts: A U.S. Marine, a Combat Photographer, and Their Journey Back from War (Viking, Aug.), he shares how his friendship with photojournalist Finbarr O’Reilly put them both on a path to recovery.

There is deep stigma attached to seeking help for mental illnesses in the armed forces, and you got plenty of grief from your fellow Marines for your insistence on getting care. What does your experience mean for other veterans and their families?

It’s people seeing that you can come out right on the other side. In the book, I described how a high-ranking officer stood up [at an event] and said that we are the generation that is making it okay to ask for help. That officer is now out of the Marine Corps and he enrolled in therapy with his wife. His life is now so much better.

What are multiple tours of duty doing to soldiers?

I know midcareer officers that are leaving active duty, five to seven years away from retirement, because the operational tempo is just too much for them. It all just comes back to asking, “Are we adequately resourcing the programs that are meant to rest and refit soldiers before you send them back out?” The military is not doing that. Every 3,000 miles you change the oil on your car. If you are just blowing through oil changes and not giving the engine the break it deserves, it’s going to seize up and just break on you.

How should the military handle issues of moral injury of war and related mental illnesses?

I understand why the military struggles with the medical requirements that they have fallen short on. It is not the entire mission of the military to fix the broken gear; it is to get back in the fight. It falls on the Department of Veterans Affairs to provide the adequate medical treatment that disabilities warrant. That said, there need to be proper channels for evaluating people.

What do you make of how the American media deals with wars and veterans issues?

I started the The War Horse because there was a lack of accountability journalism within the field. There are plenty of “the Marines got new exercise shorts” or “the Army has new nine-millimeter pistols” stories. But only two or three places write about the hundreds of millions of dollars wasted by government contractors. We want in-depth, long-form reporting that holds people accountable.