Final answer:
The Union's Military Plan during the American Civil War consisted of various components such as military strategy, organization, and service.
Step-by-step explanation:
The content of The Union's Military Plan: 3rd Component is not explicitly mentioned in the provided information. However, based on the references provided, we can infer that the military plan of the Union during the American Civil War consisted of various components such as military strategy, military organization, and military service. The plan aimed to suppress the Confederacy, repel invasions, and execute the laws of the Union.