Which military branch's birthday is celebrated on 18 September?

The birthday celebrated on 18 September is associated with the establishment of the Air Force. This date marks the creation of the United States Air Force as a separate military branch in 1947, when it was officially established by the National Security Act of that year. The Air Force operates independently from the Army and Navy, focusing on air and space operations.

Recognizing the significance of this date helps connect the historical development of the military and its branches, as well as the distinct role that the Air Force plays in national defense and aerial operations. This understanding reinforces the unique identity and heritage of the Air Force compared to other branches, which have different founding dates and roles within the military structure.