General Discussion

Gemini AI, FWIW, says (apologies for the missing formatting):

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In the United States, the President has sole authority to order a nuclear launch. This means the President does not legally require the consent of the Secretary of Defense, the Chairman of the Joint Chiefs of Staff, or Congress to authorize a strike.How the Process WorksAuthentication: To issue an order, the President must provide a unique authentication code, known as the Gold Codes, often carried on a plastic card nicknamed the "biscuit." This identifies the person as the Commander-in-Chief to the National Military Command Center (NMCC).The "Football": A military aide always accompanies the President with the Nuclear Football, a briefcase containing strike options and communication tools.No Veto: While the Secretary of Defense is required to verify that the order is authentic, they do not have the power to veto it.Potential Safeguards and ConstraintsWhile the authority is singular, the execution of the order is not. The system includes several practical and legal checks:The Two-Person Rule: Once a launch order is received at the operational level (such as a missile silo or submarine), two or more authorized individuals must independently verify the order and simultaneously turn keys or enter codes to execute it.Legal Obligation to Disobey: Under military law, service members are required to disobey "manifestly unlawful" orders. If an order to use nuclear weapons were deemed a violation of international humanitarian law or a war crime (e.g., targeting civilians without military necessity), commanders could theoretically refuse to carry it out.Recent Context: As of April 2026, there has been heightened public debate regarding this authority following escalating tensions with Iran and "Operation Epic Fury," leading some experts to call for reforms that would require additional certifications for a nuclear first strike.

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The above does not seem to support any 1/3 situation. Note especially the first two sentences.