Can a U.S. President Destroy the World If He Wants To?
No, The President cannot unilaterally decide to destroy the world. In order to launch a nuclear attack, there are many hoops, which the President needs to jump through. The procedure involves more than one person. No president can press a button on his desk and star WWIII. In fact, there is no such thing as the "nuclear button." This is a highly structured chain of command before any nuclear missile is launched. The command-and-control system is both bureaucratic as well as technical. It involves land-based missile silos, submarine-based ballistic and cruise missiles, and weapons capable of being dropped from bombers. This chain of command requires that first the president order the secretary of defense to carry out a launch. The Secretary who acts as a conduit, implements the order by linking to the military. If the President or the secretary of defense die or become incapacitated, others in line of succession take over the process.
To be sure, the details of such a process is highly classified because the government does not want the enemy to know that the procedure is, lest they will disable or defeat it. We do know that there is an aide, always following the president around with at least one (or two) large satchels known as the "nuclear football," which supposedly contain the nuclear attack information, as well as the process to verify the identity of the President, authenticate orders and effectively communicate with the military.