U.S. Marines of the 3rd batallion, 4th regiment, escort a comrade in shock after an artillery shell hit an Amtrack troop transporter during fighting with Iraqi gunmen in 2003. (Laurent Rebours/ASSOCIATED PRESS)

Roger Boas is the author of “Battle Rattle: A Last Memoir of World War II.”

A recent study by the Rand Corp. concludes that the U.S. military is unable to provide adequate therapy sessions for thousands of soldiers suffering from post-traumatic stress disorder. The February study of 40,000 cases, the largest ever, found that only a third of troops with PTSD received the minimum number of therapy sessions needed after being diagnosed. As a veteran, I am appalled.

Though my war experience was 70 years ago, it haunts me to this day. I can still remember the sound that froze my blood. The stomach-churning whistle of a field artillery round, like a thousand shrieking pigs, increasing in a ghastly crescendo until it finally explodes — and bodies fly in every direction.

Anyone who has served in ground combat knows that sound. It’s our worst nightmare. You never know where the incoming projectile is going to hit. You’re either dead or you’ve managed to squeak out alive one more time, deeply shaken. It happens nonstop, any hour of the day or night. It seeps into your bones.

They called it “shell shock” in World War I, which saw an enormous increase in the use of field artillery. Mobile cannons could shoot farther and more explosively than ever before, so they were deployed by the thousands. The shells rained for hours at a time. The only thing the soldiers in those trenches could do was duck and pray to whatever God they hoped was still listening.

What gets you is the fear. That’s what ate away at me during my months of combat as a field artillery forward observer in World War II. (I’m in my 90s now, one of the few dinosaurs still standing from that conflict.) They had dubbed its predecessor, WWI, “The War to End All Wars,” but it didn’t stop them from fighting the same war all over again 25 years later. Don’t get me wrong: WWII was a war we had to fight. (I have my doubts about some of our more recent efforts, however.) Only those of us who have been in combat know the true price of war. The lives and limbs lost. The psychological scars.

The Army spends a fortune training its troops to kill but almost nothing to train us for coming home. I spent almost two years firing 105mm howitzers across the Mojave Desert and the plains of Northern England before I was deployed in the fight against Hitler. I served in the Fourth Armored Division of Gen. George Patton’s Third U.S. Army, his spearhead into Germany, which meant 11 months of nonstop combat — and nonstop fear. Strangely, the fear would leave me entirely when I went into action; it was the unending dread of waiting to go into action that did me in. Humans aren’t wired for war. We’re survivors. We’re programmed to run from danger. When we are forced into a war zone for extended periods, it messes with our minds.

We called it “battle rattle” in my war — and I came home in 1945 to San Francisco with a bad case of it. My parents didn’t quite know what to make of me. I couldn’t make sound decisions, and my relationships suffered. No one knew what to say, so they said nothing. It took many years to feel even a semblance of “normal.”

There were tens of thousands of us. And even more after Vietnam. In the 1980s, they finally came up with a clinical diagnosis: PTSD. An alarming number of veterans suffer from it. This is not confined to modern warfare with its explosives and sophisticated weaponry. It goes back to Shakespeare and even Homer. You find it in the Book of Job and the Mahabharata from India. Here’s a speech from a worried spouse to a soldier fresh off the battlefield from Shakespeare’s “Henry IV, Part 1”:

Tell me, sweet lord, what is’t that takes from thee

Thy stomach, pleasure, and thy golden sleep?

Why dost thou bend thine eyes upon the earth,

And start so often when thou sit’st alone?

Why hast thou lost the fresh blood in thy cheeks,

And given my treasures and my rights of thee

To thick-eyed musing and cursed melancholy?

That’s a mental state that sounds a lot like my “battle rattle.” It happens every time you ask humans to kill other humans. And yet our soldiers’ reentry into society is rarely factored into the cost of war. There’s little buffer in place to help us unwind. With all the money it spends on our training, why doesn’t the Army provide training for the other side of our service: “civilian” training camps to facilitate our return to life at home? It’s not such a far-fetched idea.