An American WWII doctor told how he calmly watched US soldiers massacre German SS guards in the Dachau concentration camp because they 'SO HAD IT COMING'.

Captain David Wilsey wrote to wife Emily that he did not have a 'single disturbed emotion' because he saw the Nazis as 'SS Beasts' that deserved to be slaughtered.

GIs tortured them by making them stand for hours in Heil Hitler salutes and pouring iced water over their naked backs before they were shot dead.

Captain Wilsey also bragged about looting the camp supplies for eight days in an apparent collapse of the rule of law among the troops.

The items he stole included twin sweaters for him and his wife - it is not clear if they were from victims who died in the camp - and Swastika banners he planned to use to decorate their basement.

The letters were reported by the New Republic and come after Daily Mail Online published the details of a new book which also addressed what happened at Dachau.

They cast new light on the actions of US soldiers who were confronted with the horrors of the Nazi concentration camps and offer some insight into how battle-weary troops reacted as the full extent of the atrocities committed in Dachau - and other similar places - were revealed to them.

Eyewitness: Doctor David Wilsey, an anesthesiologist, was a US Army captain when he took part in the liberation of Dachau - then saw SS guards being killed by GIs as the horrors of the camp unfolded

Horror: This was a picture taken by Capt Wilsey in his letters to his wife, Emily. On the back he wrote: ' just a sample of what we saw & lived for days after we hit Dachau. Piles like this all over! '

Unimaginable: On the back of the picture above, Capt Wiley wrote of the corpses: 'This, madam (and all the world) is just a sample of what we saw and lived for days after we hit Dachau. Some in this pile are not quite dead. Nice? '

Capt Wiley, an anesthesiologist in the Seventh Army, had been in action for months as American and British forces advanced from Normandy to Germany.

He was decorated for his work saving GIs' lives in surgery with a bronze star. He had performed 5,000 procedures.

In terms of the time he spent in it, Dachau was a small part of his war, and his letters contained other examples of everyday heroism, writing about 'trying to save a good-looking German eight-year-old who had stepped on a mine with resultant nine holes in his intestines, half a foot off, and hundreds of minor fragments in his upper legs, arms and face'.

But his experience of Dachau is likely to be the most significant addition to the historical record.

Historians have described the massacre of dozens of SS guards at the hands of American GIs as arguably the most shameful episode in American involvement in WWII.

The troops were so outraged at the horrific scenes at Dachau, where tens of thousands of innocent prisoners were killed and 30,000 left to die, that they lost their heads - and took revenge.

The charges against those involved were dismissed by General George Paton, but history has not forgotten what happened at the end of April 1945.

The New Republic article is one of the most disturbing accounts that has made public so far and goes further than even the official investigation carried out by the Army.

It gives a fresh account of what happened when ordinary soldiers confronted the worst of Nazi evil - and had to not just deal with it immediately, but live with the psychological consequences for the rest of their lives.

At the time he helped liberate Dachau, Captain Wilsey was a 30-year-old anesthesiologist with the 116th Evacuation Hospital.

On V-E Day, May 8, 1945, he sent a seven page letter to his wife, Emily, which he began with: 'My Most Precious Being'.

It spoke of how he saw 40,000 'wrecks of humanity' walking around in what he called 'THE home of SS Bestiality'.

The letter said: 'I saw captured SS tortured against a wall [by U.S. soldiers] and then shot in what you Americans would call 'cold blood'—but Emily!

'God forgive me if I say I saw it done without a single disturbed emotion BECAUSE THEY SO HAD-IT-COMING after what I had just seen and what every minute more I have been seeing of the SS beasts' actions'.

The letter also talks about how Captain Wilsey spend three 'intensive' days and five other days looting from the camp, which he said was so full of supplies that he found more there than all the stores in downtown Chicago.

His only regret was that each soldier did not have an entire freight car each to bring their 'PHENOMENAL/STUPENDOUS!' haul back home.

Execution: An official US Army photographer captured an image which has been widely believed to be SS guards' executions in progress. Although whether this picture captures the shootings has been disputed, Capt Wiley's letters reveal an eyewitness account of GIs taking revenge on the Nazi guards

Liberation: Dachau was freed by troops of the 45th Division, 7th US Army on 30 April 1945, just days before the final collapse of the Reich. The GIs were cheered by the surviving prisoners

Doubtless, as a medic, Captain Wilsey would have been grateful for the medical supplies that the camp had, but he also looted other items.

The letter says: 'I'll only mention a few: a fine deer rifle, twin sweaters for you and I; silk smock for your house—"hasty" work; beautiful and expensive punching bag; I passed over most of the beautiful Dresden-ware; anesthesiology equipment; fine optical lens equipment (I missed the best); swords-tools-machinists apparatus; fountain pens; lotions; Swastika & SS banners to decorate our Rumpus Room, etc etc.'

It is unknown where the sweaters in particular came from. There were stores for SS soldiers but camps were also know to keep the stolen possessions of their victims.

The letters were made public by Captain's Wilsey's daughter Clarice, who lives in Eugene, Oregon; she found them in a trunk in the attic containing his old stuff.

They are being seen as invaluable as there are hundreds of them and they cover five years.

Miss Wilsey said that before he died in 1996 her father would bristle when anyone tried to deny the Holocaust and would say: 'I was there'.

He was also very taken with the film Schindler's List but refused to talk in depth about what he had seen.

The horrors of Dachau are unimaginable to most people, but Captain Wilsey saw it with his own eyes.

He saw the bodies of men weighing just 50lbs stacked on top of one another, gas chambers built like shower rooms and piles of corpses on the streets.

He also heard the awful accounts, such as one which was told to him by a Dutch resistance fighter who had been captured in 1943:

His letter to his wife said: 'A captured escapist was tied by the SS naked to a post, and three of these huge Dobermans (after four days of being starved) were turned loose on him while thousands of internees witnessed it all standing at attention.

'Hans withstood the calves torn off, withstood the thighs torn off, withstood the guts (yes, guts) turned out. But he turned his head and vomited when the Dobermans had torn the lungs and heart out.

'The first thing the liberated internees did was to shoot the Dobermans and their horrid handler.'

The effect of this on the troops is hard to comprehend, but even the most conservative accounts suggest a kind of collective madness came over the men.

In a letter sent on May 22 Captain Wilsey goes into more detail about the executions of German soldiers; far more disturbing detail.

The letter says: 'Did I 'confess' how PASSIVELY my canteen cup was used to pour icy riverwater down SSers half-naked backs as they stood for hours with a two-arm-up-Heil Hitler before being shot in cold blood?

'A truly bloodthirsty (I'd never seen it before) combat engineer from California asked to borrow my cup in performing his 'preliminaries' to roaring his .45 automatic right into the face of 3 SSers. He was bloodthirsty and nothing else would have ever 'satisfied' that boy for his brother's death at the hands of the SS.'

Never forget: Capt Wilsey wrote to his wife : 'When all other names are forgotten, Dachau will still be remembered.' Hitler died the day the camp was liberated

Freedom: Although the end of the war brought the end of Nazi horrors, the scale of the suffering at Dachau shocked the liberators. Capt Wilsey records how SS guards were shot by GIs in vengeance

The letters are published in this month's New Republic magazine

The New Republic says that Captain Wilsey's letters show another, darker side of the American GI which is rarely featured in Hollywood films.

The article notes that US soldiers have been 'been canonized as an altruistic and honorable moral opposite of our unspeakably cruel and vicious enemy'.

The article, by journalist Steve Friess, says: 'Wilsey's letters complicate that sanitized picture of the GI, revealing him instead to be what he was in real life: undeniably heroic, courageous, dutiful, dedicated, brutal, vengeful, and ethically compromised'.

According to 'Hitler's Last Day' the American soldiers who liberated Dachau went on the rampage after screaming: 'Let's get those Nazi dogs!'

The troops supposedly opened fire on 50 German with a machine gun after lining them up and saying: 'Take no prisoners!'

One commander shot dead four other Germans and became so hysterical that his own colonel had to hit him with the butt of his gun to stop him battering a fifth.

Colonel Felix Sparks of the 45th Infantry later tried to play down what was done by his men and said that most of the reports were 'wild claims'

In one account he said: 'The total number of German guards killed at Dachau during that day most certainly not exceed fifty, with thirty probably being a more accurate figure.

'The regimental records for that date indicate that over a thousand German prisoners were brought to the regimental collecting point.'

Captain Wilsey saw it differently and just a few days after liberating Dachau realized that what had happened was beyond anything mankind had ever seen.

He urged his wife to 'instill [what he saw] into as many thousand others as you can', adding in another letter two weeks later to 'JUST JAM DOWN THEIR THROATS'.