The world was possibly minutes away from nuclear war when . an American plane was shot down
a Soviet Union nuclear submarine emerged off the east coast of the United States
America threatened retaliation from Eastern Europe
Cuba was attacked by the Soviet Union

Option: an American plane was shot down

Explanation:

In the 1960s, the Soviet Union shot down a U-2 spy plane and captured Pilot Gary Francis Powers. The United States denied the aircraft used for surveillance. The Soviet, with the capture of the pilot and wreckage, declared part of the CIA. At last Dwight D. Eisenhower forced to admit that it had been spying on the Soviet. Tensions from the incident were high when Eisenhower and Russian leader Nikita Khrushchev arrived in Paris to begin a summit. Khrushchev wasted no time in blaming the United States.

they sometimes resort to unethical tactics.

the answer is states.