The major event that involved the use of atomic bombs in 1945 was the bombings of Hiroshima and Nagasaki during World War II. On August 6, 1945, the United States dropped the first atomic bomb, named "Little Boy," on Hiroshima, resulting in immense destruction and loss of life. Three days later, on August 9, the second bomb, "Fat Man," was dropped on Nagasaki. These bombings led to Japan's unconditional surrender on August 15, 1945, effectively ending World War II. The use of atomic bombs raised ethical questions about warfare and initiated the nuclear age, influencing global politics for decades ahead.