Answer
Russia and Poland
Step-by-step explanation
Brinkmanship is a technique of war of pretending that your country is going to war with another country just to make another country to retreat. This policy was applied by Dwight D. Eisenhower, the 34th president of the United States to help win his campaign for president with the goal of ending communism. This technique is common in international politics were one seeks the advantage through creation of the impression that his/her country is willing and able to apply and push a highly dangerous situation to the limit instead of conceding. Eisenhower effectively applied the brinkmanship during the Cold War. This is to mean that the countries involved were Russia and Poland. During the Cold War, threats of nuclear war and brinkmanship made both the U.S and the Soviet Union to back down.