Two atomic bombs were used against Japanese cities before Japan surrendered in 1945. The first bomb struck Hiroshima on August 6, and the second struck Nagasaki on August 9.
The Hiroshima weapon, nicknamed “Little Boy,” was a uranium gun-type bomb. The Nagasaki weapon, called “Fat Man,” used a plutonium implosion design. Both attacks caused enormous immediate destruction and long-term effects from radiation exposure, though the cities and surrounding circumstances differed.
The bombings occurred during a broader crisis for Japan. The Soviet Union declared war on Japan on August 8 and began invading Japanese-held Manchuria on August 9. Historians continue to debate the relative importance of the atomic bombings, the Soviet entry into the war, and Japan’s internal political struggle in producing surrender. The two bombings are therefore distinct events, not two names for one attack, and neither should be confused with conventional firebombing raids.