Is it possible to serve in two separate branches of the US Armed Forces?

I personally went from being a Terminal Lance in the Marine Corps to the Army National Guard. It’s hardly unusual in the Guard, there’s probably 6 or 7 former Marines in my company, a dozen old Sailors, and a sprinkling of Airman. Marines do not have to go through a transition course to join, but airmen and sailors do. It’s called the “Blue to Green” course, basically a condense basic to get them used to the different culture and to teach rudimentary combat skills. Marines are exempt and actually are automatically awarded a secondary MOS of 11B (infantryman) even if they served in a different MOS.

Nobody’s “automatically awarded a secondary MOS.”

Forgot something: Also, it’s not true that “All Marines have a secondary MOS of Infantryman.” No matter the version of that military myth you may have heard, it’s just that: a military myth.

Marines are not automatically awarded a secondary MOS of 11B. The two that I have enlisted in the last 2 months, one was awarded the MOS of 63B (wheeled vehicle mechanic) the other 91A (Abrams tank mechanic.)

And National Guard are generally exempt from repeating Basic Training.

SSG (P) Schwartz

Another anecdotal reference, but I knew many people who were former Army/Marine types in my 23 years in the Navy. My present neighbor served in three different military services, including the Canadian AF.

I went through USMC boot camp with a 27 year old guy who already served 4 years in the US Army.
On the topic of MOS… All US Marines are 0311 (rifleman) before they are trained in any other MOS. No matter what your specialty, you can always be reassigned as an infantry rifleman.

My best friend’s father was both an Army helicopter pilot and a submariner in the U.S. Navy. And yes, I’ve seen the evidence, he’s not bullshitting.

No, they are not. They are trained in the basics of the Infantry but they are not awarded, nor do they hold, the MOS. Consider the DD214 upon separation. Is it required that every Marine have listed on that the “automatic secondary MOS” you and some others assert? No. That’s because it’s not automatic and nobody is automatically awarded that MOS.

When I was in the USMC, every Marine held the 0311 infantry rifleman MOS.
When my son was in the Marines in the 90’s, the same was true. Unless there has been a change in the last few years, every US Marine holds a primary or a secondary 0311 MOS of rifleman.

Dig up your old DD214.

I did… it lists me as 0311. My son’s mos was in gauge calibration and repair working on USMC helicopters, but he also carried a 0311mos.

I’m not sure what you mean by this, but I can state from personal knowlededge that this is not true. I joined the Navy in 1987. My best friend in boot was a guy who had done 4 in the Army, got out, realized he got screwed (infantryman - apparently the job market for civilian infantrymen sucked), and joined the Navy as an aircraft mechanic. He lost one spot (left Army as E3, joined Navy as E2)., but was awarded some prior service credit. He did, however, have to take full boot, not the 3 (4?) week prior service version.

More on Blue to Green, as mentioned by JerseyMarine2092: Find Your Career in the U.S. Army | goarmy.com

I enlisted in the Army in '86, so I don’t know what the other branch’s policies on prior service was at that time. Just repeating what the recruiters told me in early '90, when I was looking at my re-enlistment options, and was shopping around.

Air Force and Navy both asserted that they were not taking Army prior service (PERIOD! But the Navy guy called me at my unit and did admit they were taking Army prior service from select MOS’s, and told me mine wasn’t one of them), and the Marines said that they’d take us, but we’d have to start back over at E-I-Owe-You-One, which, as far as I know about the U.S. Armed Forces, can’t be done willy-nilly like that. I mean, I was pretty taken back by that statement, and asked for clarification if he meant we had to do boot over again, and he emphatically stated that I’d be reduced to E-1 and have to do boot over again.

I stopped talking to him at that point.

If you feel the need to continue to disagree with what I’ve posted, be advised you aren’t disagreeing with me; you’re disagreeing with what the Air Force, Navy, and Marine recruiters in Killeen, TX, told me in March or April of 1990, and I have relayed here.

Maybe they were lying; maybe they were idiots; maybe they didn’t like Army; maybe they didn’t like me. I don’t know, and as it was 20 years ago, I no longer care enough to argue about it.

Or maybe policy changed between my experience in '87 and yours in '90. You originally made a statement about a four year period, part of which I had experience with. Now you’ve narrowed it down to a two-month period about which I have no particular information. I would hate to be characterized as calling you a liar for that.

John Warner served in the US Navy during WWII, returned to civilian life, served in the US Marine Corps during the Korean War, returned to civilian life, served as Secretary of the Navy during the Vietnam War, returned to civilian life – and then spent thirty years in the Senate, repeatedly serving as Chairman of the Armed Services Committee.