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Overview

Hiroshima devastated by a 13 kiloton nuclear explosion.

The power of fission and fusion can be unleashed in various ways to cause devastating explosions. The 13 and 21 kiloton explosions over Hiroshima and Nagasaki in August 1945 burned both cities to the ground, killing over 200,000 people instantly. Yet nuclear weapon States went on to develop far more destructive weapons that dwarf the power of these simple fission weapons. The reduced size and weight of these more advanced weapons also makes them much easier to deliver than earlier types.

STATES HAVE GONE ON TO DEVELOP WEAPONS THAT DWARF THE POWER OF THE BOMBS DROPPED ON HIROSHIMA AND NAGASAKI.
Each of the U.S. W87 warheads yields 300 kilotons.

At the height of the Cold War, thousands of U.S. and Soviet ballistic missiles on high alert were capable of delivering up to 10 independently targeted warheads at a time, each one twenty times more powerful than the Hiroshima bomb. Though decades of arms control agreements have slowly reduced the size of their arsenals, nuclear weapon States still possess the capability to destroy each other many times over.

NUCLEAR WEAPON STATES STILL POSSESS THE CAPABILITY TO DESTROY EACH OTHER MANY TIMES OVER.
The largest-ever man-made explosion: the 1961 Tsar Bomba

The largest nuclear explosion in history was the 1961 Soviet “Tsar Bomba” test, which measured more than 50 megatons (3,800 times more powerful than the Hiroshima bomb). To generate an explosion of this magnitude using dynamite, it would require 50 billion kilograms (over 110 billion pounds) of TNT, which is more than the weight of all the cargo that has passed through London’s Heathrow airport in the past 40 years. Expressed in volume, this would amount to 18 blocks of TNT each as large as the Empire State building.

IN TODAY’S UNCERTAIN WORLD, BRINGING THE COMPREHENSIVE NUCLEAR-TEST-BAN TREATY INTO FORCE SHOULD BE AN URGENT PRIORITY.
Click for animation of the CTBT's Global Alarm System.

Countries have ultimately made the decision to test nuclear devices for a number of reasons—both technical and political (World Overview: Why test?). Though basic knowledge of nuclear weapons design has become public information, the challenging task of actually building functional devices is based on trial and error. Only through nuclear testing can a country confirm that its design and engineering has been successful and gain insights for potential further development. As scientists become confident that weapons will function reliably according to their specifications, militaries are able to incorporate them into their strategic doctrines. The CTBT’s ban on nuclear testing will greatly obstruct these types of developments, and the Treaty’s verification regime will assure that a nuclear test anywhere on the planet is detected.