How can someone retire as an E5 or E6?

So many possibilities! Up-or-Out hasn't always been what it is now. In the Air Force not-so-long-ago one could retire as an E-6 at 20--may be the same today. Then there's medical retirement. There are career field limitations that might keep a person from getting beyond E-6 in 20 years. A very small career field with few openings for advancement could greatly limit opportunity.

Some of my troops made it to the "protected zone" of 17 years and were allowed to continue and retiree. Then there was an opportunity for some people to early retire at reduced retired pay in the 1990s.

LTC (Join to see) - I've seen your state several times on this thread "E4 is automatic at 24 months". Is this an Army thing? Is it true for all branches of all services? Was it true over our history?

Took me 3 years to make E4. That was at my 4-1/2 year mark and being passed over 6 times. I had to fight for my rank, get the records corrected to reflect all of my points and to get my Company CO's support as well. Making E5 took just over 6 years and I did not pin those on until my 7th year. (I attached my profile page view of my promotions.)

USMC, circa 1980s-1990s. You were promoted within your overall MOS. If the DoD said 10% can be promoted, each MOS got to promote 10%. Think what happens when you are in a glutted MOS like Communications. It was a slow promote MOS by its very nature. And all but my last 2 years was during the Cold War.

I show up to USMC Birthday Balls still. I enter the room with my SSgt stripes and 3 service stripes (4 years apiece). I mingle with SSgts who have 1 service stripe! (4 - 7.99 years) Should I be upset? Envious? Pissed? Grateful? I've felt, even but briefly, all of those emotions. But then, my experience was in a different environment and time. War tends to create a fast promote atmosphere.

Last note: R also denotes Reserves. USMCR = reserves. USMC(R) = retired.

That can be possible, and fairly common in the Reserve /NG conpnents, especially for low density MOSs

Also, every MOS is different, just because you ranked up quickly doesn't mean this is possible with every other MOS in the Army.

My dad retired from the USAF in 1964 as an E5.

As others have said some of it is driven by Medical Retirements. During the draw down in the 1980's 15 year retirement was offered in selected overstrength MOSs, since those MOSs were overstrength they had slower promotion rates meaning the retirees were lower in grade than their peers in other MOSs. At least in the Army, retention control points have varied over the years. For 2015 the last year I could find, the most popular retirement pay grade is E-7 with E-6 being the next most popular. In the Navy the pay grades were reversed with E-6 being the most popular and E-7 being the second most popular. This difference in the Navy is probably tied directly to the promotion tests. The Air Force shows almost twice as many E-7s retired as E-6s which most likely means they promote a higher percentage to E-7 than their sister services.

Slow promoting MOS, broken time etc. not that unusual. Not very common for 20 years continuous.

Well, seems someone has some sand in their nether region - votes down my comment then disables my ability to respond to his parting idiocy - Thank you for your service 1SG Furr. Your bravery in the face of internet words is truly something to be emulated. BTW - everything in my profile is verified by my 214 and ERB

I can give one real life example.
When I joined my first unit in Germany (1977) after Engineer Officer basic, I immediately met our very personable and knowledgeable unit clerk, an E-6. Seems this E-6 had been enlisted, went to OCS, went to Vietnam (a couple of tours), where he ended up with a small plate in his head. Then the major RIF in the mid seventies, and he was given the choice, get out or stay in by reverting back to an E-6 (this was a fairly common option after RIFs). So he chose to stay in to get his twenty. He did a great clerk job when on duty, but he basically didn’t give a f**k about much else (resentment was the key operative there). Would often get drunk off hours, and one time it was enough to earn an article 15 and reduction in grade to E-5. So he retired as an E-5, but his retirement pay was as a Captain over 10 years (so we were told). I felt for him because he had given a lot to the Army prior to the RIF (had a lot of awards). But sometimes in life, you get screwed. And you have to get over it and move on. Again, speaking from personal experience, both in the military and in civilian life.