The two leaders<em> wanted to prevent regions from joining the communists.</em>
Explanation:
They practised Brinkmanship to to get and advantageous position by pushing dangerous events to the brink of active conflict, it forces the opponent to back down and make concessions.
This term is associated with John Dulles. He was secretary of State during Eisenhower administration and tried to deter the Soviet Aggression by warning it of massive retaliation.
Dulles's policies were anti communist and he played an important role in formation of Southeast Asia treaty Organisation to prevent communism from spreading to other countries. He served Eisenhower from 1953 to 1959.
The Babington Plot was a plan to assassinate Queen Elizabeth I (Mary Stuart's cousin) in 1586. The plan was discovered by Sir Francis Walsingham and was used to entrap Mary (Queen of Scots) and led to her execution.