The date was 31 January, 1943. The place was the basement of the shell-shattered Univermag department store in the Soviet city of Stalingrad. And it wasn't the forlorn and exhausted faces of the Nazis that stuck in the minds of the soldiers from the Soviet Red Army, as they opened the underground warren in which Adolf Hitler's traumatised military commanders were hiding.

"The filth and human excrement and who knows what else was piled up waist high," recalled Major Anatoly Zoldatov. "It stank beyond belief. There were two toilets and signs above them both read 'No Russians allowed'."

The legendary yet horrifically decisive battle of the same name had just ended in bitter and humiliating defeat for Hitler's 6th Army. It was to be only a matter of time before Nazi Germany capitulated.

Lieutenant Colonel Leonid Vinokur was the first to spot the decorated commander of the German troops lying in a corner. "He lay on the bed when I entered. He lay there in a coat with his cap on. He had two-week-old stubble and seemed to have lost all courage," he remembered. The commanding officer was Field Marshal Friedrich Paulus.

The graphic first-hand accounts of the Volga river battle which claimed the lives of 60,000 German troops and between half a million and a million Red Army soldiers are part of a collection of hitherto unseen interviews with Russian Stalingrad combatants which have been published for the first time.

The Stalingrad Protocols has been compiled by the German historian Jochen Hellbeck, who gained access to several thousand interviews with Second World War Red Army soldiers, held in archives at the Soviet Academy of Sciences in Moscow.

The accounts, which were originally intended as a record of the Soviet Union's "Great Patriotic War" are so candid and disturbingly graphic that the Kremlin only published a small portion of them after 1945, preferring to opt for more orthodox Stalinist propaganda. The "protocols" languished in Moscow's archives until 2008, when, acting on a tip-off, Mr Hellbeck was able to gain access to 10,000 pages of them.

The accounts suggest the invading German army's murderous and brutal occupation of the Soviet Union was one of the prime motives behind the Red Army's ferocious counter-offensive. A Soviet sniper called Vasily Zaytsev tells his interviewer: "One sees the young girls, the children who hang from trees in the park – this has a tremendous impact."

Major Pyotr Zayonchovsky recalls finding the body of a dead Russian comrade who had been tortured by the Germans: "The skin and fingernails on his right hand had been completely torn off. The eye had been burnt out and he had a wound on his left temple made by a red-hot piece of iron. The right half of his face had been covered with a flammable liquid and ignited."

The first-hand accounts also bring to life the terrifying ordeals suffered by both sides in the gruelling house-to-house street fighting which dominated much of the battle. In some cases the Red Army would find itself occupying one floor of a building while the Germans held another. "In this street fighting, hand grenades, machine guns, bayonets, knives and spades are used," recalls Lieutenant General Chuikov. "They face each other and flail at each other. The Germans can't take it."

Historically, the protocols have been hailed as significant because they cast doubt on claims made by the Nazis and later by the Soviet Union's Cold War opponents that the Red Army's soldiers only fought so resolutely because they would otherwise have been executed by the Soviet secret police.

In his acclaimed 1998 account, Stalingrad, the British historian Anthony Beevor puts the number of Red Army soldiers executed by their own side during the battle at 13,000. He also points out that more than 50,000 Soviet citizens fought on the German side at Stalingrad alone. However, Soviet documents obtained during the compilation of the protocols suggest there were fewer than 300 executions by mid October 1942 – three and a half months before the German defeat.

Whether some of the interviews were given purely for Soviet propaganda purposes remains open to question. Those given by political officers suggest they played an important role in providing the inspiration to fight. There are accounts of them distributing leaflets during the height of battle depicting "the hero of the day". Brigade Commissar Vasilyev recalls: "It was viewed as a disgrace if a Communist was not the first to lead the soldiers into battle."

Hellbeck notes in his edition of the protocols that on the Soviet side at Stalingrad, the number of card-carrying Communist party members rose from 28,500 to 53,500 between August and October 1942 and that the Red Army saw itself as politically and morally superior to its Nazi opponent. "The Red Army was a political army," he told Der Spiegel magazine.