There is a significant risk of nuclear weapons being used in the future.  Estimates of the consequences of nuclear war are highly based on a number of unknowns, but they still provide insight into the seriousness of the nuclear threat.  If the United States and the Soviet Union had fought a direct nuclear war during the Cold War, it is estimated that hundreds of millions of people would have likely been killed by nuclear attacks.  Even with the much lesser nuclear proliferation around the world, there is still a risk of regional atrocities.  If a nuclear weapon were used in a major urban center, billions of people would be at risk of radiation exposure and fallout.  In fact, the nuclear detonations above Japanese cities during World War II, known as the nuclear bombing of Hiroshima and Nagasaki, resulted in the deaths of hundreds of thousands of people from fallout exposure and related illnesses.
assistant
In a recent 2017 study, a group of prominent scientists and scholars conducted an analysis of the probability of nuclear weapons being used in the future.  Their findings were that this risk is one of greatest risks in the coming decade, both in terms of its probability and impact.  Nuclear weapons have been used three times so far in history: the first was 1945 by the United States in the atomic bombings of Hiroshima and Nagasaki, the second was in 1998 during the U.S. intervention in Kosovo, and the third was by India and Pakistan in 1998 against each other.  The risk of nuclear weapons use in the coming decade were conducted under various assumptions of nuclear weapons using governments.  They found that the risk of interstate nuclear violence was large and ongoing and could increase substantially in the coming decade.  Details of the study are included in this report: www.worldacademy.org/content/the-future-of-nuclear-weapons
assistant
How many countries possess nuclear weapons?
user
Right now, there are nine nuclear weapon-possessing countries in the world: The United States, Russia, France, the United Kingdom, China, India, Pakistan, North Korea, and Israel.  And some non-declared nuclear weapons states, such as South Africa, also existed at certain points in time.  The treaties and policies that control the spread and use of nuclear weapons are collectively known as the nuclear non-proliferation regime.  This set of agreements is aimed at preventing the spread of nuclear weapons from existing nuclear weapon-possessing countries to new states and also preventing weapon states from using their weapons.
assistant
What treaties are you referring to that prevent the spread of nuclear weapons?
user
The first such agreement was the Nuclear Non-Proliferation Treaty, or NPT.  This treaty was signed in 1970 and had a total of 189 signatory states when it entered into force in March 1970.  The treaty is a multilateral pact that commits signatory states not to create or acquire nuclear weapons.  A group of five nuclear weapons states — the United States, France, Russia, the United Kingdom, and China — were each committed to moving towards nuclear disarmament and regionalizing nuclear weapons separately.  States that were not signatories to the treaty were committed to international negotiations.  The treaty has been severely criticized for their unfair provisions.  Adherence to the treaty is required for an unarmed state to benefit from the treaty’s research, safety, and financial benefits.  As a result, the treaty has not prevented the spread of nuclear weapons among some countries and non-signatory states that already possess nuclear weapons.  The treaty has also struggled to work with states that are “threshold” nuclear weapons states, countries with significant capabilities to produce nuclear weapons, but have not been verified as doing so.
assistant
What is the risk of nuclear weapons being used in the future?
user