The relationship between college education and military officer dates back to 1802 and the founding of West Point. At the time there was significant debate over whether having a standing army was compatible with the values of a republic, particularly given how issues like the quartering of British soldiers played in the decision to declare independence. The idea of the period was to have a corp of trained officers who would lead an expanded army, thus the prevalence of West Pointers in the higher ranks of the military in the Mexican War and the Civil War.

The Civil War marked a turning point in that it expanded the idea that a standing army was necessary to the maintenance of federal power and as a result students land-grant universities from the Morrill Act of 1861 had to engage in military training. This process lasted through the 1950s. Despite the increased emphasis on federal power the standing army remained small, so when a major conflict occurred there was still a significant need to expand the officer and NCO corps. The bubble test played a large part of this.

In the wake of WWII and the birth of the Cold War, U.S. defense spending increased significantly over traditional peacetime norms and the standing army increased by an order of magnitude. More officers from ROTC received active commissions and the need to create officers out of new recruits diminished significantly. The move to the all volunteer army furthered this, as the idea was to have an active and reserve force capable of fighting two wars simultaneously, requiring a more formal process for the training and development of officers.

The bubble test still exists in some forms as the ASVAB which helps place new recruits into their military occupational specialty, and the ability of people to enlist with an option to go to OCS following basic training.

Just to clarify something, in the current US Military, is having a Degree the only criteria to be selected for 'Officership'?