If you have neither, you don't qualify for military service. 20 years ago the Army was the only service left that would take non-HS grads, but since the military has become a very technical place to work, even the Army changed their policy in the '80's.
For both the Naval Reserve and Active Duty Navy you need either a High School Diploma or a GED - at least per official regulations.
In reality though, unless your ASVAB scores are off the charts, the current recruiting and retention climate (retention is always high and recruiting is low during bad economic times as everyone wants to join the military or government) means that unless you show exceptional aptitude, they'll opt for a H.S. graduate before a GED recruit. They will look at the circumstances of your GED though - if you couldn't finish HS for personal reasons (had to take care of a family member, etc.) then that's a major consideration. But most people get a GED because they dropped out and finished later, and in the military's eyes that shows a lack of commitment, and that reflect on the potential recruit's personality. It's difficult in a recruiting environment where the branches can pick only the best recruits available.
Your entrance exam scores are really the key - as an example, I was a fairly average student in HS (wasn't challenging enough), but scored very high on the ASVAB. I had recruiters bugging me for months until I finally joined.
My point is that there are many reasons that people don't finish school, and as long as it doesn't fall into the category of "school sucked so I quit", then a GED isn't necessarily a negative.
Finish High School.
You need high school equivalency. Go for your GED.
College ROTC commissions Reserve, National Guard, and Active Duty officers. You may choose which one you want.
no you can't join the armed forces while you are in high school
You can join JROTC.
18 years old is the minimum age required to join the Navy ROTC.
US army accepts new recruits with high school or equivalent education. Yes you can join army with your high school diploma.
Walt Disney didn't attend college. He didn't even finish high school. He dropped out to join try and join the army in WWI. He was underage and never served in the military, but he did manage to lie about his age and join the Red Cross as an ambulance driver at the tail end of the war.
You need either a diploma or a GED, and a GED may require college credit hours in addition.
They join the mile high club after school.
To enter the US Air Force regardless of component (Active Duty, Reserve, National Guard) you will need either a high school dimploma or GED.
Walt Disney didn't attend college. He didn't even finish high school. He dropped out to join the army.