Jimmy Stewart suffered such extreme PTSD after being a fighter pilot in World War II that he acted out his mental distress during 'It's a Wonderful Life'.

Stewart played George Bailey in the classic movie and channeled his anger and guilt into the scenes where he rages at his family.

Stewart was haunted by 'a thousand black memories' from his time as an Air Force commanding officer that he took with him back to Hollywood after the war.

Pilots who flew with him said that became 'Flak Happy' during World War II, a term to describe what is now known as Post Traumatic Stress Disorder, or PTSD.

Stewart wrestled with the guilt of killing civilians in bomb raids over France and Germany including one instance where they destroyed the wrong city by mistake.

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Actor Jimmy Stewart, pictured in 1945 after World War II combat ended, was haunted by his memories from his time in the Air Force

Before entering the military, Stewart earned his commercial pilot license so that he could join the Air Force. Pictured above, a base intelligence officer shows Captain Stewart (right) maps before he begins a mission in WWII

Stewart suffered such extreme PTSD from WWII that he acted out his mental distress during 'It's a Wonderful Life'

He would would channel his PTSD while filming scenes for the film, including the above scene on the bridge

Stewart felt responsible for the death of his men and especially one bloodbath where he lost 13 planes containing 130 men who he knew well.

Stewart's anguish is laid bare for the first time in author Robert Matzen's Mission: Jimmy Stewart and the fight for Europe, published by Paladin Communications.

Stewart never spoke about it, even to other veterans, and bottled up his emotions that came out in the acting parts he chose when he returned to Hollywood.

He acted it out during It's a Wonderful Life, where character George Bailey unravels in front of his family - the emotional core of the film after a lifetime of setbacks, including being unable to go to war while his brother becomes a decorated hero.

Films like Shenandoah and Winchester 73 allowed Stewart to explore his dark side which was never there before he went to war.

Matzen writes that Stewart's decision to join the military was less surprising than his decision to become an actor; his grandfather fought in the Civil War and more distant relatives fought in the Revolutionary War.

Growing up in Indiana, Pennsylvania, he got into acting while in school and was given a contract by MGM in 1935 which led to him starring Philadelphia Story in 1940, for which he won the Oscar.

Stewart's initial attempts to join the military failed because he was too skinny. Pictured above, he's wrapped in layers while experiencing winter in Europe. His bulk includes long johns, a blue bunny heated flying suit, shirt, tie, pants, coveralls, jacket, scarf and gloves

Stewart's chance came with the creation of a B-24 bomber group, the 445th, and he was appointed commander of the 703rd squadron. After their air medal mission to Pas de Calais, the crew of the B-24H known as Lady Shamrock pose with air commander Stewart

Following the war, Stewart struggled to find work until director Frank Capra hired him for It's A Wonderful Life (Stewart pictured above in a scene from the film)

However in his spare time Stewart was flying planes relentlessly and got his commercial pilot license so that he could join the Air Force.

His initial attempts failed because he was too skinny, despite trying to fatten himself up on ice cream and chocolate bars.

Stewart was finally called up shortly before the assault on Pearl Harbor in 1941 which forced America into the World War II.

Asked by a studio boss why he wanted to give up his life in Hollywood, Stewart said: 'This country's conscience is bigger than all the studios in Hollywood put together, and the time will come when we'll have to fight'.

Stewart was initially put in the Air Force Motion Picture Division because commanders wanted to use him to make films to convince more airmen to sign up.

He was also used for PR stunts until he demanded that he see combat like other airmen.

Stewart's chance came with the creation of a B-24 bomber group, the 445th, and he was appointed commander of the 703rd squadron.

Fellow actor Clark Gable (right, with Stewart) also entered the military and was sent into combat

Comparison photos show the price of service. In the photo at left, Second Lieutenant Stewart poses in early 1942. The photo at right shows Major Stewart two years later, after having flown three months of maximum effort combat missions as a squadron commander

Stewart was put in command of a B-24 bomber group, the 445th. A B-24 with the circle F (pictured above) denoted the 445th Bomb Group

Matzen writes that the 'key moment in Jim's life had arrived. There would never be another like this, not before, not after'.

Speaking to DailyMail.com, Matzen said that Stewart signed up because he 'felt he had to prove himself, especially with women, to prove he was attractive enough, charming enough'.

He said: 'He wanted to prove he was responsible enough, that's the key with him. He wanted to prove he was responsible enough to be an officer, that he could handle this, he could make his dad proud of him'.

According to 'Mission', Stewart and the 445th were deployed to Tibenham in East Anglia in England where they would carry out bombing raids on German targets.

Stewart did not stay on the ground and flew with his men.

Unlike other commanding officers Stewart, who was a Captain, took time to get to know his men as he wanted a team atmosphere.

The tactic worked but at a huge personal cost - when they started to be killed off it hit him harder.

Their first mission was to bomb a Nazi submarine facility in the city of Kiel and went off better than Stewart had expected.

Not flying was difficult than flying for Major Stewart, seen here waiting on the control tower platform at Station 124 Tibenham for the group to return from a mission

Stewart refused to discuss his combat missions and remained aloof about his service until the end of his life. In 1976 he returned to Tibenham, England, where he spent four months as a squadron commander

As the flight got underway Stewart's dream was finally realized - he was in combat.

Matzen writes that he 'became part of something vital, something like the phalanx of the Roman legions'.

The biggest shock was the flak from anti-aircraft guns.

Matzen writes that the training about it 'bore no resemblance to the experience' and their bombers yawed left and right and pitched up and down as explosions went off all around them in the sky.

None of Stewart's planes were shot down during the raid - but soon the bodies began fall.

During a raid on Bremen, the second largest port in Germany, enemy fighters took down a bomber called 'Good Nuff'. Of the crew of ten, just three parachuted out.

Not for the first time, Stewart had to write a letter to the parents of the dead airmen saying they were missing and presumed dead.

A mission over Mannheim ended in catastrophe when they lost two planes with 20 men inside.

And as the weeks went on, this all began to weigh heavily on Stewart.

Matzen said: 'He was a perfectionist and he was so hard on himself. It wasn't just that he had responsibility for his plane, if he was in a group it was 15-20 planes and it was sometimes 75-100 planes.

In March 1942, one month after winning the Academy Award as Best Actor for his role in The Philadelphia Story, Stewart is inducted into the US Army in Los Angeles

'It just got to him and it got to him pretty fast.

'Every decision he made was going to preserve life or cost lives. He took back to Hollywood all the stress that he had built up.'

In total Stewart flew 20 missions and the stress manifested itself physically and mentally.

Stewart could not keep his food down which became a problem when he was embarking on draining eight or nine hour missions.

Stewart survived the war on peanut butter and ice cream which meant his diet consisted of just protein and sugar.

Unable to sleep, he became more and more wore down by the demanding flights - that became more and more bloody.

The worst was one that Stewart did not actually fly on, but his squadron did.

The raid on the city of Gotha, Germany, led to the loss of 13 planes, or 130 men all in one go.

Those who survived told horrific tales of bodies flying through the air and planes exploding in front of them.

More more than two hours Nazi fighters 'poured death and destruction' at Stewart's men from every direction.

They used cables with bombs attached to them to bring their bombers down, fired rockets 'like the Fourth of July' and fired rockets at will.

Nazi pilots followed the planes as they went down to make sure there were no survivors.

Stewart heard all this and knew that the next day he had to lead the next nearly identical mission.

That night he did not sleep - miraculously his flight was nowhere near as bad.

Perhaps the episode which disturbed Stewart the most was a raid which went terribly wrong.

The 453rd were assigned to bomb a V-1 rocket facility in the northern French village of Siracourt.

It's A Wonderful Life (pictured, with Stewart center) was a lifeline for Stewart and rehabilitated him in the eyes of Hollywood, showing directors that he could still act

The instruments in Stewart's cockpit malfunctioned and 12 bombers deployed their payloads on the city of Tonnerre instead.

At least 30 tons of general purpose bombs rained down causing unknown numbers of civilian casualties.

Stewart's pilots tried to cover for him but he took the blame himself, something which earned him their ultimate respect.

In all Stewart had served four-and-a-half years during World War II and was awarded the Air Medal with oak leaf clusters, Distinguished Flying Crosses and the Croix de Guerre.

Matzen told DailyMail.com that he interviewed one of the pilots who flew with Stewart who told him that Stewart once said that he had gone 'flak happy' and was sent to the 'flak farm'.

'Flak happy' refers to what has now become known as PTSD but was little understood at the time, while the 'flak farm' was a treatment center for soldiers.

Matzen's book, Mission: Jimmy Stewart and the Fight for Europe, hits bookstores on October 24 and is available for order on Amazon

After getting a leave of absence Stewart spent weeks staying with his friend Peter Fonda in Los Angeles doing nothing but decompress.

Matzen writes that Stewart 'couldn't imagine life in a peacetime air force, settling into a routine of drudgery'.

For Stewart his soul had been 'ground down to nothing' and his 'youth had died'.

When Stewart's mother Bessie and his father Alex saw him for the first time they were 'shocked by what they saw - their boy had aged what seemed decades'.

Matzen writes that he was a decorated war hero, was rake thin and had gray hair and a 'command authority' that made his father uneasy.

Stewart faced a grim reality: He was 37 but looked 50 and his career as a romantic lead was over. He struggled to find work until director Frank Capra hired him for It's A Wonderful Life.

Matzen said that it was a lifeline for Stewart and rehabilitated him in the eyes of Hollywood, showing directors that he could still act.

Speaking to DailyMail.com, Matzen said: 'Jim came back from hell on earth and groped around for a movie to make, and his only offer he had was for what would become the most beloved motion picture in all American culture.

'In an unlikely life full of unlikely things -this gangly stringbean becoming a movie star and then a war hero -this was the unlikeliest.'

The movie also provided an unlikely outlet for his still raw emotions.

Matzen said: 'I don't think he had that kind of capacity before the war. It enabled him to be ferocious and to have that raw emotion.

'You see it time and time again; I think he would look for scripts where he could demonstrate that rage. I think that was the side of him that in there all the time and that's how he would let it out,'

Stewart did not leave the military and continued to serve until May 1968 when he retired after 27 years of service during which time he was a bomber pilot during the Vietnam War.

But the memories of World War II never left him and he would see people in the street who reminded him of the airmen who had died under his command.

In 'Mission', Matzen writes: 'Was he still flak happy, on a flak farm? Who could tell what was real after all that had happened over five long years.

'The nightmares come every night.

'There was on oxygen at 20,000 feet with 190s zipping past, spraying lead and firing rockets, flak bursting about the cockpit. B-24s hit, burning, spinning out of formation.

'Bail out! Bail out! Do you see any chutes? How many chutes? Whose ship was it? Oh God, not him?

Not them! Bodies, pieces of bodies smacking off the windshield.

'And the most frequent dream, an explosion under him and the plane lifted by it and the feeling that this was the end.'



