Donald Trump has raised international concerns by alleging that Pakistan is conducting covert nuclear weapons tests, although no proof has been presented. In a dramatic interview, he also accused Russia, China, and North Korea of similar activities and asserted that the United States should restart its own testing activities “because others are conducting tests.” Both Pakistan and China have strongly denied these claims. Experts in nuclear security warn that such statements could ignite a risky new arms race. Could this signal the end of the nuclear testing moratorium?