The Katyn massacre cover up has been a longstanding debate among leaders around the globe but a new testimony uncovered by the Minister of Culture finally brought to light the truth behind the killing of 22,000 Polish soldiers in 1940.

“For us, the most painful aspect is that from 1944-1952, covering up the truth about Katyn was a political decision – it was not accidental,” Minister Zdrojewski told the press as he unveiled the decades-old document on Wednesday.

“During that time, so much determination was devoted to the matter – including threats against specific people – that the truth about Katyn was unable to see the light of day,” he added regarding the Katyn massacre cover up.

In 1943, Hitler's Nazi government declared news that it had uncovered mass graves in the Katyn Forest near Smolensk, Russia where around 4,000 Polish soldiers were buried.

More than 20,000 Polish officers and members of the elite had been reported missing in 1940 after reportedly being held captive by the Soviets.

The document discovered by the Minister of Culture contains a testimony made by Lieutenant John H. Van Vliet from May 10, 1945. Vliet was one of many Allied prisoners of war held in captivity and brought to Katyn by the Germans in 1943.

The Germans had made the Allied POWs their witnesses, confirming evidence that their enemies, the Soviets, had committed the crime. Thus the legacy of the Katyn massacre cover up began.

In the several years that followed, the American and British governments tried to stop information of Soviet guilt from leaking to the masses, so as not to upset the partnership with Russia.

Moscow cut ties with the Polish government-in-exile in England, after it called from a Red Cross investigation and pacifist leader Stalin claimed that Germany had carried out the Katyn massacre of 1940.

The POW's testimony reveals personal details of British prisoners who were captured and taken as witnesses to the Katyn exhumations, and whose names were reportedly suppresed by Allied Forces.

Van Vliet said in his testimony that some of the corpses discovered in the mass grave had been found with documents or mementos that said that they had been murdered in February, March and April 1940, indicating the period before Germany occupied the Smolensk area.

The prisoner also indicated in his letter that the soldiers' remains involved in the Katyn massacre cover up seemed as though they could have been there for more than three years.

“For a moment, I started to think that it was a mirage, that I was hallucinating,” said Krystyna Piorkowska, the academic who discovered the document in November 2013 in the State Archives of the United States in Washington. “I was slightly afraid that no one would believe that such a thing exists.”

Russian government had admitted guilty for the Katyn massace of 1940 in 1990. The mass murder and burials took place at several locations across the Soviet Union.