Final answer:
President Eisenhower believed that the United States could keep itself safe from foreign threats by implementing a policy of brinkmanship, which involved being willing to go to the brink of war and using nuclear weapons if necessary to defend the country.
Step-by-step explanation:
President Dwight D. Eisenhower believed that the United States could keep itself safe from foreign threats by employing a policy called brinkmanship. Brinkmanship involved the United States being willing to go to the brink of war and even using nuclear weapons if pushed too far by other countries. This policy aimed to deter potential aggressors by demonstrating American resolve and the willingness to defend itself.