[dragoon500ly]

A brief overview:

The United States was the first country to manufacture nuclear weapons and is the only country to have used them in combat, with the bombings of Hiroshima and Nagasaki in World War II. Before and during the Cold War, it conducted 1,054 nuclear tests and tested many long-range nuclear weapons delivery systems.

Between 1940 and 1996 the U.S. spent an estimated $10.1 trillion in 1997 dollars on nuclear weapons, including platforms development (aircraft, rockets, and facilities), command and control, maintenance, waste management, and administrative costs. At its peak (1967), the U.S. possessed 31,255 warheads. The current U.S. arsenal (2021) is some 3,750 warheads plus an additional estimated 2,000 warheads that have been retired and are awaiting dismantlement.

Since its first use in 1945, the President of the United States has had the responsibility for the sole authority to launch U. S. nuclear weapons, whether as a first strike or nuclear retaliation. This arrangement was seen as necessary during the Cold War to present a credible nuclear deterrent; if an attack was detected, the United States would have only minutes to launch a counterstrike before its nuclear capability was severely damaged, or national leaders killed. If the President has been killed, command authority follows the presidential line of succession. Changes to this policy have been proposed, but currently, the only way to countermand such an order before the strike was launched would be for the Vice President and the majority of the Cabinet to relieve the President under Section 4 of the Twenty-fifth Amendment to the United States Constitution.

Regardless of whether the United States is actually under attack by a nuclear-capable adversary, the President alone has the authority to order nuclear strikes. The President and the Secretary of Defense form the National Command Authority, but the Secretary of Defense has no authority to refuse or disobey such an order. The President's decision must be transmitted to the National Military Command Center, which will then issue the coded orders to nuclear-capable forces.

Dating back to the Eisenhower administration, the authority to launch a full-scale nuclear attack has been delegated to theater commanders and other specific commanders if they believe it is warranted by circumstances, and are out of communication with the president or the president had been incapacitated. An example of this would be the Cuban Missile Crisis, when General Thomas Power, commander of the Strategic Air Command, took the country to DEFCON 2, the very precipice of full-scale nuclear war, launching the SAC bombers of the US with nuclear weapons ready to strike.

It has been a long-standing U. S. policy of “no first use” of nuclear weapons. Indeed, the U.S. has stated "will not use or threaten to use nuclear weapons against non-nuclear weapons states that are party to the NPT [Nuclear Nonproliferation Treaty] and in compliance with their nuclear nonproliferation obligations", this promise covers more than 180 countries. This policy is known as a “negative security assurance.” This policy was confirmed under President Trump’s 2018 Nuclear Posture Review (NPR).

HOWEVER, China, the Soviet Union (and now Russia), and North Korea do not fall under the US negative security assurance. China and Russia are nuclear weapon states under the NPT, and North Korea withdrew from the treaty in 2003 and conducted its first nuclear test in 2006.

This means that they could be targets for US nuclear weapons, including the United States launching weapons at them first.

Both the Obama and Trump administration NPRs state that the U.S. “would only consider the use of nuclear weapons in extreme circumstances to defend the vital interests of the United States or its allies and partners.” However, the Obama version stated that use would be limited to “a narrow range of contingencies” and emphasized that the goal was to continue to “reduce the role of nuclear weapons in deterring non-nuclear attacks, with the objective of making deterrence of nuclear attack on the United States or our allies and partners the sole purpose of US nuclear weapons.”

The Trump NPR broadens the definition of “extreme circumstances,” saying these “could include significant non-nuclear attacks. Significant non-nuclear attacks include, but are not limited to, attacks on the U.S., allies, or partner civilian population or infrastructure, and attacks on U.S. or allied nuclear forces, their command and control, or warning and attack assessment.” This could potentially include cyber attacks as a valid reason for nuclear use under US policy.

I hope you've enjoyed this long, dry, and sometimes confusing overview of the U.S. policies concerning NBC Warfare. Primary source materials are the Congressional Records and the Congressional Research Service.