Bear with me; this won't be very brief, and I'll be honest.
In 1967 the USA was involved in the Vietnam war. I was turning 18 and compelled by law to register for the military draft. EVERYONE starts out as "1-A" (Available for unrestricted military service).
Of course as a JW I was told I was a conscientious objector to military service, so I applied for a "1-O" deferment (Conscientious objector to all military service. A registrant must establish to the satisfaction of the board that his request for exemption from combatant and noncombatant military training and service in the Armed Forces is based upon moral, ethical or religious beliefs which play a significant role in his life and that his objection to participation in war is not confined to a particular war. The registrant is still required to serve in civilian alternative service.) on these grounds and after face-to-face meetings with the local Selective Service Board in Long Island City, New York (located in Queens, NYC). I was given my "1-O" after my solo appearance before the board. But the Watchtower wanted us to avoid "alternative service" so my "1-O" was not good enough.
What I really needed, I was told, was a MINISTERIAL deferment, a "4-D". (Minister of religion, formally ordained by a recognized religion, and serving as a full-time minister with a church and congregation). I became a PIONEER, and my goal hours were 100 per month. During the time I pioneered my overall average hours per month were slightly less than this. I was also a ministerial servant in the Middle Village congregation. I got my "4-D".
I married in 1971 and as the "head of a household" I had to work full time and I stopped pioneering. My monthly hours became substantially reduced.
In 1973 the USA withdrew from Vietnam, having suffered more than 58,000 casualties.
Within the cessation of registrant processing in 1976, all registrants (except for a few alleged violators of the Military Selective Service Act) were classified "1-H" (Registrant NOT currently subject to processing for induction or alternative service) regardless of any previous classification.
By that time - 1976 - I was well into fading out and becoming what is now known as a "POMO." My monthly hours were zero.