British historian Simon Sebag Montefiore states that Soviet terror in the occupied eastern Polish lands was as cruel and tragic as the Nazis' in the west. Soviet authorities brutally treated those who might oppose their rule, deporting by 10 November 1940 around 10% of total population of Kresy, with 30% of those deported dead by 1941.[99] They arrested and imprisoned about 500,000 Poles during 1939–1941, including former officials, officers, and natural "enemies of the people" like the clergy, but also noblemen and intellectuals. The Soviets also executed about 65,000 Poles. Soldiers of the Red Army and their officers behaved like conquerors, looting and stealing Polish treasures. When Stalin was told about it, he answered: "If there is no ill will, they [the soldiers] can be pardoned".[100]

In one notorious massacre, the NKVD-the Soviet secret police--systematically executed 21,768 Poles, among them 14,471 former Polish officers, including political leaders, government officials, and intellectuals. Some 4,254 of these were uncovered in mass graves in Katyn Forest by the Nazis in 1943, who then invited an international group of neutral representatives and doctors to study the corpses and confirm Soviet guilt, but the findings from the study were denounced by the Allies as "Nazi propaganda".

TLDR: The Soviet occupations surrounding WWII were brutal, fascist, and borderline genocidal. Suggesting they were great fun for all involved is completely disgusting.