Which document described the threat that civilization itself was at stake due to Soviet values?

The correct answer is NSC-68, which was a key document in the history of U.S. foreign policy during the Cold War. Released in 1950, NSC-68 articulated the perceived threat of communism and the Soviet Union to not just U.S. interests but to the broader concept of Western civilization. It emphasized that the Soviet challenge was not merely a military threat but also a fundamental ideological one, positing that the survival of freedom and democracy was at risk as long as totalitarian regimes existed.

NSC-68 called for a significant increase in military spending and a more aggressive stance towards containment of communism, reflecting the belief that the United States needed to counter the Soviet influence globally. The document underscored the urgency of the situation, indicating that allowing the spread of Soviet values would jeopardize the future of liberty and democracy in the world.

This context makes NSC-68 the pivotal document highlighting the existential threat of the Soviet ideology, which is why it is the correct answer.