My son made sargeant within two years of enlisting in the Marine Corp. He went on to become an ambassador's aide when he developed diabetes and was given a medical discharge. He was devastated as he had planned to make the corp his career.
Tell him: thanks.
That reminds me of my two year enlistment between 1966-68. I was in a small "cadre" unit that had a bunch of us with weird MOS's. Due to the rapid growth of the Corps during that Vietnam buildup period, a couple of Intelligence PFC's zipped thru Lance Corporal, Corporal and went to Sergeant E-5...needless to say, the much senior (in time) who suddenly found themselves outranked were dumbfounded.
One guy was a Logistics MOS and he actually made Staff Sergeant in his two years...unbelievable.