Final answer:
Racism in the military was influenced by World War I segregation, Korean War racial tensions, and Vietnam War discrimination, reflecting broader societal trends and impacting the Civil Rights movement.
Step-by-step explanation:
Historical events that contributed to racism in the military include World War I segregation policies, Korean War racial tensions, and Vietnam War discrimination. Therefore, the correct option is Option 4: All of the above. During World War I, African Americans served in segregated units and experienced discrimination both as soldiers and on the home front. The Korean War saw African American soldiers, including the highly commended 2nd Ranger Company, encounter challenges due to their racial identity. The Vietnam War marked the first major conflict with fully integrated units, yet substantial equality issues persisted, leading to significant racial tension and riots within the military. The military has often mirrored the larger societal trends of racism ongoing in the United States and played a role in shaping the African American Civil Rights movement.