Little Boy was the first nuclear weapon used in warfare, dropped on Hiroshima on 6 August 1945, killing tens of thousands instantly.
Key Facts
- Explosive yield
- ~15 kilotons of TNT kilotons TNT
- Explosion radius
- ~1.3 km km
- Uranium charge
- 64 kg total; <1 kg fissioned kg
- Delivery aircraft
- Boeing B-29 Superfortress Enola Gay
- Weapon type
- Gun-type fission (uranium-235)
- Weapons completed by 1950
- At least 5 (all retired Nov 1950)
By the Numbers
Location
Cause → Event → Consequence
During World War II, the United States pursued nuclear weapons through the Manhattan Project. The gun-type Little Boy design, developed at Los Alamos Laboratory by Lt. Cmdr. Francis Birch's group, was chosen after the plutonium-based Thin Man design was abandoned in 1944 due to technical problems. Its relative simplicity gave designers confidence it would function without prior testing.
On 6 August 1945, the B-29 Enola Gay dropped the uranium bomb designated L-11 (Little Boy) over Hiroshima, Japan. It detonated with roughly 15 kilotons of force and an explosion radius of approximately 1.3 kilometres, causing widespread death and destruction across the city. It was the first nuclear weapon ever used in combat and the second nuclear explosion in history after the Trinity test.
The bombing of Hiroshima, followed days later by the Fat Man detonation over Nagasaki, accelerated Japan's surrender and the end of World War II in the Pacific. After the war, additional Little Boy-type bombs were manufactured; at least five were completed by 1950, though all were retired by November of that year as more advanced designs replaced them.
Belligerents & Mobilization Analysis
Side A
1 belligerent
Francis Birch.
Side B
1 belligerent