What significant change occurred in 1947 regarding the Air Force?

The significant change that occurred in 1947 regarding the Air Force was the authorization of the United States Air Force as a separate branch of the U.S. military. This event marked a critical transition in the structure of the United States Armed Forces, as the Air Force was previously part of the U.S. Army and was reestablished as its own independent service through the National Security Act of 1947.

The establishment of the Air Force allowed for the development of air power strategies and capabilities distinct from those of the Army and Navy. This autonomy enabled the Air Force to focus on its unique mission, including aerial combat, nuclear deterrence, and strategic bombing, thereby enhancing the United States' overall military effectiveness during the Cold War and beyond.

In contrast, the other options highlight concepts that either developed later or were not part of the pivotal moment in 1947 when the Air Force gained its independence and authority as a separate entity. Special operations forces, joint command structures, and advanced surveillance systems evolved in different contexts and times, reflecting subsequent advancements in military strategy and technology.