I'm in the US Navy currently. Been in for about a year now, I finished basic training on my 23 birthday, but I had thoughts of joining the marines as a younger man. I'm so grateful that I went to uni for a few years. I have a much better perspective on life and what I'm sacrificing for than many of my comrades.
My joining was not just to serve my country; that is a huge part, but I joined to better myself. To push myself out of my shell, to give me unique experiences and to work with some of the most awe-inspiring machines and quality people.
I thought a lot about how I could best serve my country, and carrying a rifle wasn't it. There is a need for that and if that is what you truly want to do, get some uni experience or at least wait a few years.
just my 2 cents.