May 1, 1960: The U-2 incident takes place.
By 1955, both the United States and Soviet Union had developed and successfully detonated thermonuclear weapons; the next year, the first Lockheed U-2, an icon of Cold War-era espionage, flew a mission over the Soviet Union in order to gather and deliver intelligence regarding its technological progress. Covert reconnaissance missions conducted throughout the era provided the government detailed photographs that would, hopefully, enable the U.S. to stay ahead of its communist foe.
Meanwhile, Soviet Union-United States relations seemed to be, to some extent, thawing - in late 1959, Nikita Khrushchev visited the United States for the first time with his family (and a strong desire to see Disneyland) and left the country in the hope that some kind of détente might be achieved between the nations. This brief period of good feelings was disrupted by the U-2 incident, in which CIA pilot Francis Gary Powers and his U-2 spy plane were shot down while flying in Soviet airspace. Unaware that both the pilot and his equipment had been recovered by Soviet officials, the U.S. government released a cover story claiming that Powers had been conducting weather tests. The cover story was contradicted by the concrete evidence provided by the Soviet government of American espionage activity, and by Powers’ own confession; Powers, upon returning home (having been traded for a KGB agent), was criticized for failing to self-destruct his aircraft and for failing to commit suicide, although he was ultimately determined to have not divulged any important information to the Soviets and was posthumously awarded the Silver Star in 2012.
Although Eisenhower accepted responsibility for the incident, including the failed cover-up, the U-2 incident caused the collapse of the planned Paris Four Power summit, and any tentative easing of tensions achieved in the previous decade was undone. And in 1962, a U-2 plane captured images in Cuba and initiated a confrontation that would send the two nations closer to nuclear war than ever before.