Before the Commonwealth was inaugurated, the American authorities pay little attention to the Philippine's need for an adequate defense system. In 1921, the Wood-Forbes mission called the attention to the need for an "adequate locale organization of the Philippine people for the defense of the islands against aggression" and recommended to the U.S. administration that it should "at once take the necessary steps to organize, train and equip such a force".

In the early part of the 1930's, however, the fear of foregin aggression, notably Japan, led the Commonwealth to consider the problem of national security an urgent one, which must take priority over other problems in the Philippines. In 1936, the National Assembly passed the National Defense Act (Commonwealth Act No. 1) requiring all able-bodied Filipinos to undergo military training for defense purposes in times of national emergency or external invasion.

President Manuel L. Quezon requested and obtained the services of General Douglas MacArthur in formulating the defense system. MacArthur, who had by this time retired as Chief of Staff of the United States Army responded to Quezon's request. The appreciative President conferred upon the doughty General the title "Field Marshall of the Philippine Army".

As a military adviser to the commonwealth and chief of the United States military mission to the Philippines, MacArthur, with the assitance of Major Dwight Eisenhower, was largely responsible for the country's defense system.

MacArthur's defense plan envisioned the organization of a citizen army composed of two forces: a regular force, including the Philippine Constabulary, and a reserve force that would increase each year through a continuos program of training 21-year old able-bodied men for a period of five and a half months. Preparatory Military Training (PMT) in the elementary and high school levels and the Reserve Officers Training Course (ROTC) in the collegiate level would help supplement the regular government training given the recruits.

On September 3, 1936, the University of Santo Tomas School Senate (nowadays known as Student Council) approved the steps to organize the ROTC making Military Science and Tactics cumpolsory to every able-bodied male student of the university, thus giving birth to the UST Golden Corps of Cadets.