Final answer:
The National Security Act of 1947 led to formal training for Security Police, emphasizing the development of a strong defense force capable of both military action and domestic security, including new agencies like the CIA and Department of Defense.
Step-by-step explanation:
The important career field milestone that resulted in formal training for Security Police was the enactment of the National Security Act of 1947. This act reorganized the U.S. military and established new agencies focused on national defense and security, including the Central Intelligence Agency (CIA) and the National Security Council, culminating in the creation of the Department of Defense. These developments necessitated rigorous training for security personnel, not only in terms of physical readiness but also in understanding the complexities of national and domestic security. Military police and security personnel now receive formal training, which includes exposure to non-lethal measures such as being pepper sprayed, to understand the effects and foster greater restraint in its application.
Post-9/11, the awareness of internal threats led to further emphasis on domestic security, resulting in the creation of the Department of Homeland Security and demanding even more specialized training. The focus on comprehensive security strategies underscores the importance of a well-trained military and civilian security apparatus.