Which department primarily manages the physical transmission of classified information?

The primary management of the physical transmission of classified information falls under the Department of Defense. This department is responsible for ensuring that sensitive national security information is protected and securely transmitted according to established protocols. The DoD has specialized systems and methodologies in place to handle the transmission of classified materials, ensuring that they remain secure from any potential unauthorized access or compromise.

The other departments, while they may handle classified information relevant to their respective domains, do not have the same overarching responsibility as the Department of Defense regarding the physical transmission of this information. The Department of State deals primarily with foreign affairs and diplomacy, the Department of Justice focuses on law enforcement and legal matters, and the Federal Bureau of Investigation conducts investigations and enforces federal laws. Although their roles may intersect with classified information, they are not centrally tasked with its transmission in the context of national defense as is the case with the DoD.