Final answer:
The second letter from the USSR in the movie 'Thirteen Days' suggests that Soviet leaders were more concerned with their security and stability than with armed confrontation. This conclusion aligns with recent research based on declassified documents that reveal the Soviet Union's focus on its interests rather than aggression towards the United States.
Step-by-step explanation:
The second letter from the USSR in the movie 'Thirteen Days' suggests the conclusion that Soviet leaders were primarily driven by concerns for their security and stability. The letter implies that the Soviet Union was not interested in armed confrontation with capitalist nations but rather desired to promote and expand communism throughout the world. This interpretation aligns with recent scholarship based on declassified documents, which reveals a nation focused on its interests rather than aggressive intentions towards the United States.