In late 2022, the US began “preparing rigorously” for Russia potentially striking Ukraine with a nuclear weapon, in what would have been the first nuclear attack since Hiroshima and Nagasaki. What led the Biden administration to reach such a startling assessment was a collection of developments, analysis, and highly sensitive new intelligence. Russia was losing ground inside Ukrainian sovereign territory, not inside Russia. US officials were concerned Russian President Vladimir Putin saw it differently. He had told the Russian people that Kherson was now part of Russia itself, and, so, might perceive a devastating loss there as a direct threat...