What organization manages military traffic, land transportation, and common-user ocean terminals within the United States?

The US Military Surface Deployment and Distribution Command (SDDC) is the organization responsible for managing military traffic, land transportation, and common-user ocean terminals within the United States. This command plays a critical role in ensuring the smooth movement of military equipment and supplies, facilitating both peacetime and wartime logistics operations.

SDDC oversees the transportation of military cargo by land and sea, coordinating with various transportation modes to optimize the movement of materiel to support military readiness and operations. Their efforts are crucial in developing and maintaining a seamless logistics environment, managing both intermodal transportation services and operational readiness across various military branches.

The other organizations mentioned have specific responsibilities that do not encompass the entirety of military traffic and transportation. For example, the US Air Force's Air Mobility Command primarily focuses on air transportation, while the Defense Logistics Agency manages supply chains and logistics support but does not handle transportation operations directly. The US Navy's Military Sealift Command operates specific sealift vessels but does not cover all aspects of military land transportation or ocean terminal management. Hence, SDDC's comprehensive focus on surface deployment and distribution solidifies its role as the correct answer.