Final answer:
In 1960, a U.S. spy plane was shot down over the Soviet Union, leading to increased tension between the two nations.
Step-by-step explanation:
In 1960, a U.S. spy plane was shot down over the Soviet Union, leading to a significant tension between the two nations, a period known as the U-2 Affair. The spy plane, known as a U-2, was on an intelligence-gathering mission and carried equipment to photograph military installations. The pilot was captured by the Soviets, escalating the conflict between the U.S. and the Soviet Union.