you are partially correct, chisoxfn.
If you have a degree, you can either enlist or you can apply for OCS, to become an officer. I have a degree, but I enlisted.
There are some advantages to enlisting in the Army, some benefits you might not get if you the officer route, that's why I chose to enlist.
As for the Marines, I would tell you this. If you decide to go to college and not enlist, by your junior year of college, let them know you want to go to Marines OCS. I talked to the Marines before the Army, and they told me that currently they are looking for Juniors and Seniors in college, to get them ready when they graduate. So, if you wait until you graduate, they might not take you.