Myself, and all I know, had a 4 year IRR.
My bad.
National Guard folks usually do a 6 by 2, IIRC.
Isn’t it 2 years IRR and then the last 2yrs some other military term, but still officially under the authority of DOD if something goes sideways?
It was 6 years during Nam ...
I think when I joined it a combined 8 year commitment (4+4 or 6+2)