Final Answer:
The event that set a precedent for armed forces to support federal authority was the U.S. Civil War.
Step-by-step explanation:
The U.S. Civil War (1861-1865) marked a pivotal event in American history, and it played a crucial role in establishing a precedent for armed forces to support federal authority. Prior to the Civil War, the balance between federal and state authority was a contentious issue. However, the conflict served as a definitive test of the federal government's ability to maintain its authority and preserve the Union. The Union forces, representing the federal government, engaged in a military campaign against the secessionist Confederate states, emphasizing the supremacy of federal authority over state autonomy.
The outcome of the Civil War solidified the principle that federal authority was supreme, and armed forces played a decisive role in upholding this authority. The conflict resulted in a strengthened federal government and a clearer understanding of the limitations on state autonomy. The Union victory underscored the commitment to a united nation under the authority of the federal government, and subsequent events, such as the Reconstruction era, further reinforced the precedent set during the Civil War. This historical turning point not only shaped the trajectory of the United States but also influenced the development of federalism and the role of the armed forces in supporting federal authority.
In summary, the U.S. Civil War set a precedent for armed forces to support federal authority by establishing the federal government's supremacy over state autonomy. The conflict played a vital role in shaping the understanding of federalism and contributed to the evolution of the United States as a united and federally governed nation.