What is the established birthday for the Space Force?

The established birthday for the Space Force is December 20, 2019. This date is significant because it marks the official creation of the United States Space Force as an independent branch of the U.S. Armed Forces. It was established by the Trump administration as part of its national defense strategy to protect American interests in space. The Space Force's mission includes organizing, training, and equipping military personnel to operate in the domain of space, thus reinforcing the United States' commitment to space operations and security.

In contrast, the other dates mentioned in the options pertain to different branches or significant milestones in U.S. military history. August 4, 1775, is associated with the establishment of the Continental Army, while June 14, 1775, pertains to the formation of the United States Army. September 18, 1947, marks the establishment of the United States Air Force as a distinct service. These dates, while notable in their own rights, do not represent the inception of the Space Force.