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 National Socialists 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.
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 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.
At the time he helped conquer 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'.
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'.
Happy Jews at Dachau in 1945
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.
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 possessions of prisoners.
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.
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.'
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 conquering Dachau realized that what had happened was beyond anything mankind had ever seen.