nuclear weapon

Introduction & Top Questions
Principles of atomic (fission) weapons
- The fission process
- Critical mass and the fissile core
- Gun assembly, implosion, and boosting
Principles of thermonuclear (fusion) weapons
- The fusion process
- Basic two-stage design
- Enhanced designs
The effects of nuclear weapons
- Blast
- Thermal radiation
- Initial radiation
- Residual radiation and fallout
- Electromagnetic pulse
The first atomic bombs
- Discovery of nuclear fission
- Producing a controlled chain reaction
- Founding the Manhattan Project
- Selecting a weapon design
- Racing to build the bombs
- The weapons are used
The first hydrogen bombs
- Origins of the “Super”
- Policy differences, technical problems
- The Teller-Ulam configuration
- The weapons are tested
- Further refinements
The spread of nuclear weapons
- The Axis powers
- The United Kingdom
  - Atomic weapons
  - Thermonuclear weapons
  - The British deterrent force
- The Soviet Union
  - Atomic weapons
  - Thermonuclear weapons
- France
- China
- India
- Pakistan
- Israel
- South Africa
- North Korea
- Other countries
  - Taiwan
  - Argentina and Brazil
  - Libya
  - Iraq
  - Iran

References & Edit History Quick Facts & Related Topics

Images, Videos & Interactives

U.S. hydrogen bomb test in the Marshall Islands

World War II: total destruction of Hiroshima, Japan

M65 atomic cannon

Nuclear submarine

Nuclear fission and fusion

Teller-Ulam bomb design

For Students

World War II: total destruction of Hiroshima, Japan

nuclear weapon summary

nuclear weapon: Facts & Related Content

Written and fact-checked by The Information Architects of Encyclopaedia Britannica

Last Updated: Nov 11, 2025

Facts

Also Known As	thermonuclear weapon • atomic weapon

Photos and Videos

U.S. hydrogen bomb test in the Marshall Islands

World War II: total destruction of Hiroshima, Japan

M65 atomic cannon

Nuclear submarine

Nuclear fission and fusion

Teller-Ulam bomb design

View footage of the first test of a hydrogen bomb carried out by the United States in the Marshall Islands

Watch U.S. B-29 Superfortress Enola Gay decimate Hiroshima with a nuclear bomb in the Pacific War

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Topics

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Key People

Atal Bihari Vajpayee

Atal Bihari Vajpayee

prime minister of India

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Yuly Borisovich Khariton

Russian physicist

Lord Noel-Baker.

Philip John Noel-Baker, Baron Noel-Baker

British statesman

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David Lange

prime minister of New Zealand

Alva Myrdal.

Alva Reimer Myrdal

Swedish diplomat

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Raja Ramanna

Indian nuclear physicist

Bertrand Russell

Bertrand Russell

British logician and philosopher

Teller, Edward

Edward Teller

Hungarian-born American physicist

Abdul Qadeer Khan

Abdul Qadeer Khan

Pakistani scientist

Freeman Dyson

Freeman Dyson

American physicist

A.P.J. Abdul Kalam

A.P.J. Abdul Kalam

president of India