What was the secret event in 1945?

The secret event in 1945 refers to the development and eventual use of atomic bombs by the United States during World War II, specifically under the Manhattan Project. This top-secret program culminated in the bombings of Hiroshima on August 6 and Nagasaki on August 9, leading to Japan's surrender and the end of the war. The event marked a significant turning point in military history and international relations, ushering in the nuclear age.