A slump-shouldered grunt sits before a military psychiatrist, staring vacantly at a wall.

“I seen too many of my buddies gone. I figured the next one was for me,” he says softly. “A man can only stand so much.”

A veteran of the Battle of Fallujah, diagnosed with post-traumatic stress disorder? No, a veteran of the European theater in World War II, suffering from “shell shock.”

Such eerie then-and-now parallels abound in legendary director John Huston’s long-suppressed 1946 documentary, “Let There Be Light,” a gripping look at the mental health issues of troops returning from war.

The film, the final chapter in the famous trilogy that Huston made for the Army in the 1940s, has been brilliantly remastered in both picture and sound and rereleased by the National Film Preservation Foundation.

Long before PTSD entered the national vocabulary, Huston shot close to 70 hours of film at a Long Island military hospital — no staged scenes, with the cameras running continuously — to come up with his 58-minute classic.

The most powerful scenes come early: heartbreaking interview sessions with damaged young men who can barely look another person in the eye or speak above a whisper as they grope for words to describe their trauma.

“Are you aware that you are not the same boy you were when you went over? Do you feel changed?” a doctor asks a soldier who appears almost semi-catatonic.

A mumble: “Yes.”

“In what way?”

Long pause. “I used to always like to have fun. I used to always be going places. I don’t like to do nothing no more.”

Ill or injured service members now wait an average of 394 days to move through the military’s disability evaluation process, an increase of more than 10 percent since 2010 and well off the goal of 295 days, according to the Government Accountability Office.

In fiscal 2011, just 19 percent of active-duty service members and 18 percent of National Guard and Reserve members completed the Integrated Disability Evaluation System, or IDES, process within the goal of 295 days for active-duty members and 305 days for Guard and Reserve personnel.

And at some installations, the average wait is nearly 18 months or longer. At Fort Belvoir, Va., for example, soldiers face an average processing period of 537 days, while guardsmen at Fort Carson, Colo., wait 651 days.

“Now that the joint system has been implemented nationwide, I have to say I am far from convinced the departments have implemented a disability evaluation process that is truly transparent, consistent or expeditious,” Sen. Patty Murray, D-Wash., who chairs the Senate Veterans’ Affairs Committee, said at a hearing Wednesday.

IDES was introduced in 2007 to streamline the disability evaluation process and integrate the Defense and Veterans Affairs department systems.

Before IDES, service members waited an average of 450 days to get through both the required Defense Department medical exams and the separate VA process to evaluate service members for benefits to which they may be entitled.

In fiscal 2008, with IDES operational at a fraction of the 139 total military treatment facilities, average wait time was 297 days.

But that figure has steady ticked upward since the new system went force-wide.

Last year, defense officials told the Senate Armed Services Committee it might be two years before DoD and VA reached their 295-day goal; on Wednesday, the senators learned the average processing time continues to lengthen.

But VA and DoD officials said changes underway, including new IT systems and additional staff, should move the process in the desired direction.

“We’re down to production numbers where we believe we will be processing 2,500 [people] a month. If we can sustain that starting in August, we can move forward,” VA Chief of Staff John Gingrich said.