Who is the first one atomic power in the world?

The first country to develop and test an atomic bomb was the United States. This was achieved during World War II as part of the Manhattan Project, with the first successful test occurring on July 16, 1945, at the Trinity site in New Mexico. Following this, the U.S. dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki in August 1945, leading to Japan's surrender and the end of the war.