What significant change did the National Security Act bring to US governance?

The National Security Act, enacted in 1947, fundamentally transformed the structure of U.S. military and intelligence operations, ultimately leading to significant enhancements in military intelligence capabilities. By creating the National Security Council and the Central Intelligence Agency, the act established a framework that allowed for better coordination among military branches and improved national intelligence operations, which were crucial during the Cold War era. This expansion of military intelligence capacity was essential for responding to global threats and gathering information that could inform U.S. policy and military strategy. It marked a shift towards a more proactive and organized approach to national security, illustrating the growing importance of intelligence in U.S. governance.

The options that suggest decentralization, the elimination of the Department of Defense, or a focus exclusively on domestic policies do not align with the primary objectives of the National Security Act, which aimed at centralizing authority and enhancing federal capabilities in the domain of national security.