Final answer:
The Presidential Unit Citation was authorized by Executive Order 9981, issued by President Harry Truman in July 1948, to end military segregation and ensure equal opportunity.
Step-by-step explanation:
The Presidential Unit Citation was authorized by Executive Order 9981, which was issued in July 1948 by President Harry Truman. This executive order was a significant act in the fight for civil rights, as it declared an end to segregation in the military. Moreover, the order mandated that all members of the armed forces were to be given equal opportunity without regard to race, ethnicity, religion, or national origins, thereby promoting diversity and inclusivity within the military ranks.