The Manhattan Project (1942–1946) was a secret U.S.-led program with British and Canadian support designed to develop the world's first atomic weapons during World War II [1][2]. The project was driven by urgent fear that Nazi Germany was pursuing its own nuclear bomb [2]. To achieve this goal, the program pursued several interconnected objectives: understanding and controlling sustained nuclear chain reactions; producing fissile materials—enriched uranium-235 and plutonium-239—at industrial scale; and designing a reliable weapon capable of delivering a prompt nuclear explosion [1][2]. The project coordinated scientists, engineers, and industry across multiple sites including Los Alamos, Oak Ridge, and Hanford [1]. It successfully produced the first tested nuclear device at Trinity in July 1945 [1][2], and the weapons were subsequently used against Japan in August 1945 [2].