Does anyone know how often he would have re-enlisted in the military to pay off his medical education? And how often are the reenlistments? Aren’t they like every four years?
He wasn't enlisted, he was an officer. He signed a contract that said the government would pay for his medical school, and in return, he'd have an obligation to serve for "x" period of years. It can vary depending on what kind of physician you are (and how much training the govt. pays for) but it's usually 4-6 years of active duty, with a reserve obligation of anywhere from 2-4 years after that.
He wouldn't sign any other document other than his first candidate and service contract.
This muslim was a major...he was commissioned, not enlisted, so he would not have had a term of enlistment so to speak...the expiration date on his ID card would have said "INDEF". Officers in the normal accessions branches (i.e. infantry, armor, quartermaster, military police, etc.) usually incur an 8 year obligation...for West Pointers, it's a max of five years active, 3 reserve. For ROTC scholarship, it's 4 and 4, and ROTC non-scholarship, it's 3 and 5. The "Professional" branches (i.e. Doctors, Dentists, JAG Lawyers and Chaplains) are managed somewhat differently, but typically, they incur the normal obligations outlined above + an additional 2 years active duty for each year of post-graduate education.
There may be some exceptions but this is the general rule of thumb.
Hasan is a commissioned officer. They serve at the pleasure of the CIC—they don’t have to reenlist like the enlisted do.