The Cuban missile crisis
Even after many reassurances made by the Soviet Union that they were only sending defensive weapons to Cuba, in reality, things were completely different. Their true intentions were to plant their missiles on the island.
However, the secret came out the moment an American U-2 spy plane discovered and photographed various missiles being sneaked into Cuba. Then, on October 22, President John F. Kennedy made an announcement that the Soviets had stationed missiles, which were capable of carrying nuclear warheads, only 90 miles off the American coastline.
The Soviet Union tried to conceal the missile sites with different tarps, nets, paint, and mud, but their attempts failed.