The Western Allies had an implicit, if unwilling, hand in the cover-up in their endeavour not to antagonise a then-ally, the Soviet Union. The resulting Polish-Soviet crisis was beginning to threaten the vital alliance with the Soviet Union at a time when the Poles' importance to the Allies, essential in the first years of the war, was beginning to fade, due to the entry into the conflict of the military and industrial giants, the Soviet Union and the United States. In retrospective review of records, both British Prime Minister, Winston Churchill and US President, Franklin D. Roosevelt were increasingly torn between their commitments to their Polish ally, the uncompromising stance of Sikorski and the demands by Stalin and his diplomats.
In private, Churchill agreed that the atrocity was likely carried out by the Soviets. According to the notes taken by Count Raczyński, Churchill admitted on 15 April 1943 during a conversation with General Sikorski: "Alas, the German revelations are probably true. The Bolsheviks can be very cruel." However, at the same time, on 24 April 1943 Churchill assured the Soviets: "We shall certainly oppose vigorously any 'investigation' by the International Red Cross or any other body in any territory under German authority. Such investigation would be a fraud and its conclusions reached by terrorism." Unofficial or classified UK documents concluded that Soviet guilt was a "near certainty", but the alliance with the Soviets was deemed to be more important than moral issues; thus the official version supported the Soviet version, up to censoring the contradictory accounts. Churchill's own post-war account of the Katyn affair is laconic. In his memoirs, he quotes the 1944 Soviet inquiry into the massacre, which predictably found that the Germans had committed the crime, and adds, "belief seems an act of faith." In 1943, the Katyn Manifesto which blamed the Soviet Union, was published in London (in English) by the eccentric poet Count Geoffrey Potocki de Montalk. He was arrested by the Special Branch and imprisoned.
In the United States, a similar line was taken, notwithstanding that two official intelligence reports into the Katyn massacre were produced that contradicted the official position. In 1944 Roosevelt assigned his special emissary to the Balkans, Navy Lieutenant Commander George Earle, to compile information on Katyn, which he did using contacts in Bulgaria and Romania. Earle concluded that the massacre was committed by the Soviet Union. Having consulted with Elmer Davis, the director of the Office of War Information, Roosevelt rejected the conclusion (officially), declared that he was convinced of Nazi Germany's responsibility, and ordered that Earle's report be suppressed. When Earle formally requested permission to publish his findings, the President issued a written order to desist. Earle was reassigned and spent the rest of the war in American Samoa.
It would be a good thing for all of us if the UK and US publically repudiated their stances on their coverup of the events at Katyn and other locations throughout Eastern Europe. Sure I understand that sometimes the necessities of war make for some difficult decisions but......the war is long over.