The war in Ukraine has underlined the importance of religion, and especially its instrumentalization by authoritarian regimes in the conflicts of the 21st century. Religion denounced as the “opium of the people” (Marx & Hegel “Critique of Philosophy of Law”, 1843), during the Soviet regime, was also used by the secret police who infiltrated both Orthodox and Catholic Churches in the countries belonging to the USSR influence. Religion has always been a weapon of «soft power» among authoritarian regimes. During World War II, the silence and attitude of Pope XII, who did not denounce the Nazi regime, was finally clearly analysed. Religious leaders have been implicit allies of the worst regimes in Europe forgetting the teachings of the fifth commandment, “Thou shalt not kill”